Grafted thermoplastic compositions and fabricated articles therefrom

ABSTRACT

This invention describes grafted blend compositions, processes for their preparation and fabricated articles, especially foams therefrom. The blends exhibit enhanced melt strength, melt elongation greater than or equal to about 20 mm/s, increased upper service temperature, increased modulus, and increased hardness. The grafted blend compositions have little or no high shear viscosity increase over a corresponding polymer of the same chemical composition absent the coupling agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/728,245, filed Dec. 1, 2000 now U.S. Pat. No. 6,395,791 which claimsthe benefit of U.S. Provisional Application No. 60/168,702 filed on Dec.3, 1999 in the name of Bharat I. Chaudhary et al.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

The present invention relates to grafted thermoplastic blendcompositions and articles fabricated therefrom. The grafting of thepolymers generally results in improvements in one or more of meltstrength, hardness, modulus, upper service temperature in the resultingblends, over and above what is observed for the correspondingnon-grafted blends. Furthermore the grafted blends may in turn beblended with additional thermoplastic polymers to further enhance one ormore other properties. The various grafted blend compositions are usefulin the preparation of a variety of fabricated articles including, butnot limited to, foams, films, fibers, extrusion coatings, calandered andmolded articles.

BACKGROUND OF THE INVENTION

Cross-linking or coupling of polymers has been used as a method ofrheology modification of the polymer. As used herein, the term “rheologymodification” means change in melt viscosity of a polymer as determinedby dynamic mechanical spectroscopy (DMS). Cross-linking is typicallyemployed to increase the melt strength of the polymer while maintainingthe high shear viscosity (that is viscosity measured at a shear rate of100 rad/sec by DMS). Thus a molten cross-linked polymer exhibits moreresistance to stretching during elongation at low shear conditions (thatis viscosity measured at a shear of 0.1 rad/sec by DMS) and does notsacrifice the output at high shear conditions.

Various coupling agents may be employed to rheology modify and graftpolymers. Such coupling agents include peroxides, silanes, and azides.Use of poly(sulfonyl azide) to react with polymers is known, forinstance the teachings of U.S. Pat. Nos. 3,058,944; 3,336,268; and3,530,108 include the reaction of certain poly(sulfonyl azide) compoundswith isotactic polypropylene or other polyolefins by nitrene insertioninto C—H bonds. The product reported in U.S. Pat. No. 3,058,944 iscrosslinked. The product reported in U.S. Pat. No. 3,530,108 is foamedand cured with cycloalkane-di(sulfonyl azide) of a given formula. InU.S. Pat. No. 3,336,268 the resulting reaction products are referred toas “bridged polymers” because polymer chains are “bridged” withsulfonamide bridges. The disclosed process includes a mixing step suchas milling or mixing of the sulfonylazide and polymer in solution ordispersion then a heating step where the temperature is sufficient todecompose the sulfonylazide (100° C. to 225° C. depending on the azidedecomposition temperature). The starting polypropylene polymer for theclaimed process has a molecular weight of at least 275,000. Blendstaught in U.S. Pat. No. 3,336,268 have up to about 25 percent ethylenepropylene elastomer. Similarly, the teachings of Canadian patent 797,917include rheology modification using from about 0.001 to 0.075 weightpercent polysulfonyl azide to modify homopolymer polyethylene and itsblend with polyisobutylene.

It would be highly desirable to have a polymer composition of enhancedmelt strength, melt elongation greater than or equal to about 20 mm/s,increased upper service temperature, increased modulus, and increasedhardness. Preferably, the polymer compositions would have little or nohigh shear viscosity increase over a corresponding polymer of the samechemical composition absent coupling agent.

In particular, it would be highly desirable to have a polymercomposition of enhanced melt strength, and melt elongation greater thanor equal to about 20 mm/s, that can be used to fabricate variousarticles including foams. Such foams should exhibit at least one of, (1)increased upper service temperature, (2) increased compressive strengthat a specific foam density, or (3) increased hardness.

BRIEF SUMMARY OF THE INVENTION

This invention describes grafted blend compositions, processes for theirpreparation and fabricated articles, especially foams therefrom. Theblends exhibit enhanced melt strength, melt elongation greater than orequal to about 20 mm/s, increased upper service temperature, increasedmodulus, and increased hardness. The grafted blend compositions havelittle or no high shear viscosity increase over a corresponding polymerof the same chemical composition absent the coupling agent.

BRIEF DESCRIPTION OF THE DRAWINGS

Not applicable.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

All references herein to elements or metals belonging to a certain Grouprefer to the Periodic Table of the Elements published and copyrighted byCRC Press, Inc., 1989. Also any reference to the Group or Groups shallbe to the Group or Groups as reflected in this Periodic Table of theElements using the IUPAC system for numbering groups.

Any numerical values recited herein include all values from the lowervalue to the upper value in increments of one unit provided that thereis a separation of at least 2 units between any lower value and anyhigher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to 90,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which are lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

The term “interpolymer” is used herein to indicate a polymer wherein atleast two different monomers are polymerized to make the interpolymer.This includes copolymers, terpolymers, etc.

The term “melt processing” is used to mean any process in which thepolymer is softened or melted, such as extrusion, pelletizing, molding,thermoforming, film blowing, compounding in polymer melt form, fiberspinning, and the like.

The term “melt strength” refers to the maximum force attained beforesignificant draw resonance or breakage occurs when pulling strands ofmolten polymers at constant acceleration until draw resonance orbreakage occurred. The velocity at which draw resonance or breakageoccurred is defined as the “melt elongation” (the test method isdescribed herein). Unless otherwise specified, both melt strength andmelt elongation are measured at 190° C.

As used herein the term “grafted blend composition” means a polymerblend composition further comprising a coupling agent, with the provisothat the resulting grafted blend has a gel content (as determined inaccordance with ASTM D-2765-84) which is 50 percent or less, preferably40 percent or less, more preferably 30 percent or less, even morepreferably 20 percent or less, most preferably 10 percent or less.

As used herein the term “alkenyl aromatic homopolymers, or copolymers”include homopolymers and copolymers derived from alkenyl aromaticcompounds such as styrene, alphamethylstyrene, ethylstyrene, vinylbenzene, vinyl toluene, chlorostyrene, and bromostyrene. A preferredalkenyl aromatic polymer is polystyrene. Minor amounts ofmonoethylenically unsaturated compounds such as C₂₋₆ alkyl acids andesters, ionomeric derivatives, and C₄₋₆ dienes may be copolymerized withalkenyl aromatic compounds. Examples of copolymerizable compoundsinclude acrylic acid, methacrylic acid, ethacrylic acid, maleic acid,itaconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethylacrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate,vinyl acetate and butadiene.

For purposes of this invention, an alkenyl aromatic polymer is amelt-processable polymer or melt processable impact-modified polymerhaving at least 50%, preferably at least about 70% and most preferablyat least 90% of its weight in the form of polymerized vinyl aromaticmonomers as represented by the structure:

H₂C═CRAr

wherein R is hydrogen or an alkyl radical that preferably has no morethan three carbon atoms and Ar is an aromatic group. R is preferablyhydrogen or methyl, most preferably hydrogen.

Suitable aromatic groups Ar include phenyl and naphthyl groups. Thearomatic group Ar may be

substituted. Halogen (such as Cl, F, Br), alkyl (especially C₁-C₄ alkylsuch as methyl, ethyl, propyl and t-butyl), C₁-C₄ haloalkyl (such aschloromethyl or chloroethyl) and alkoxyl (such as methoxyl or ethoxyl)substituents are all useful. Styrene, para-vinyl toluene, α-methylstyrene, 4-methoxy styrene, t-butyl styrene, chlorostyrene, vinylnaphthalene and the like are all useful vinyl or vinylidene aromaticmonomers. Most preferably, the alkenyl aromatic polymer material iscomprised entirely of alkenyl aromatic monomeric units. Suitable alkenylaromatic polymers include those derived from alkenyl aromatic compoundssuch as styrene, alpha-methylstyrene, etc. Examples of copolymerizablecompounds include acrylic acid, methacrylic acid, acrylonitrile, etc.

The alkenyl aromatic polymer may be a homopolymer of a vinyl aromaticmonomer as described above. Polystyrene homopolymers are the mostpreferred alkenyl aromatic polymers. Interpolymers of two or more vinylaromatic monomers are also useful.

Although not critical, the alkenyl aromatic polymer may be characterizedas having a high degree of syndiotactic configuration; i.e., thearomatic groups are located alternately at opposite directions relativeto the main chain consisting of carbon-carbon bonds.

Homopolymers of vinyl aromatic polymers that have syndiotacticity of 75%r diad or greater or even 90% r diad or greater as measured by 13C NMRare useful herein. The alkenyl aromatic polymer may also containrepeating units derived from one or more other monomers that arecopolymerizable with the vinyl aromatic monomer. Suitable such monomersinclude N-phenyl maleimide; acrylamide; ethylenically unsaturatednitriles such as acrylonitrile and methacrylonitrile; ethylenicallyunsaturated carboxylic acids and anhydrides such as acrylic acid,methacrylic acid, fumaric anhydride and maleic anhydride; esters ofethylenically unsaturated acids such as C₁-C₈ alkyl acrylates andmethacrylates, for example n-butyl acrylate and methyl methacrylate; andconjugated dienes such as butadiene or isoprene. The interpolymers ofthese types may be random, block or graft interpolymers. Blends ofinterpolymers of this type with homopolymers of a vinyl aromatic monomercan be used. For example, styrene/C₄-C₈ alkyl acrylate interpolymers andstyrene-butadiene interpolymers are suitable as impact modifiers whenblended into polystyrene. Such impact-modified polystyrenes are usefulherein.

In addition, suitable alkenyl aromatic polymers include those modifiedwith rubbers to improve their impact properties. The modification canbe, for example, through blending, grafting or polymerization of a vinylaromatic monomer (optionally with other monomers) in the presence of arubber compound. Examples of suitable rubbers are homopolymers of C₄-C₆conjugated dienes such as butadiene or isoprene; ethylene/propyleneinterpolymers; interpolymers of ethylene, propylene and a nonconjugateddiene such as 1,6-hexadiene or ethylidene norbornene; C₄-C₆ alkylacrylate homopolymers or interpolymers, including interpolymers thereofwith a C₁-C₄ alkyl acrylate. The rubbers are conveniently prepared byanionic solution polymerization techniques or by free radical initiatedsolution, mass or suspension polymerization processes. Rubber polymersthat are prepared by emulsion polymerization may be agglomerated toproduce larger particles having a multimodal particle size distribution.

Preferred impact modified alkenyl aromatic polymers are prepared bydissolving the rubber into the vinyl aromatic monomer and any comonomersand polymerizing the resulting solution, preferably while agitating thesolution so as to prepare a dispersed, grafted, impact modified polymerhaving rubber domains containing occlusions of the matrix polymerdispersed throughout the resulting polymerized mass. In such products,polymerized vinyl aromatic monomer forms a continuous polymeric matrix.Additional quantities of rubber polymer may be blended into the impactmodified polymer if desired.

Commercial HIPS (high impact polystyrene), ABS(acrylonitrile-butadiene-styrene) and SAN (styrene-acrylonitrile) resinsthat are melt processable are also useful as blend components of thepresent invention.

The alkenyl aromatic polymer has a molecular weight such that it can bemelt processed with a blowing agent to form a cellular foam structure. Anumber average molecular weight of about 60,000 to about 350,000,preferably from about 100,000 to about 325,000 is suitable. In the caseof an impact-modified polymer, these molecular weight numbers refer tomolecular weight of the matrix polymer (i.e., the continuous phasepolymer of an alkenyl aromatic monomer).

The term “substantially random” (in the substantially randominterpolymer comprising polymer units derived from ethylene and one ormore α-olefin monomers with one or more vinyl or vinylidene aromaticmonomers and/or aliphatic or cycloaliphatic vinyl or vinylidenemonomers) as used herein means that the distribution of the monomers ofsaid interpolymer can be described by the Bernoulli statistical model orby a first or second order Markovian statistical model, as described byJ. C. Randall in POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method,Academic Press New York, 1977, pp. 71-78. Preferably, substantiallyrandom interpolymers do not contain more than 15 percent of the totalamount of vinyl aromatic monomer in blocks of vinyl aromatic monomer ofmore than 3 units. More preferably, the interpolymer is notcharacterized by a high degree of either isotacticity orsyndiotacticity. This means that in the carbon⁻¹³ NMR spectrum of thesubstantially random interpolymer the peak areas corresponding to themain chain methylene and methine carbons representing either meso diadsequences or racemic diad sequences should not exceed 75 percent of thetotal peak area of the main chain methylene and methine carbons.

The “substantially random interpolymers” can be prepared by polymerizingi) ethylene and/or one or more α-olefin monomers and ii) one or morevinyl or vinylidene aromatic monomers and/or one or more stericallyhindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, andoptionally iii) other polymerizable ethylenically unsaturatedmonomer(s). Suitable α-olefins includes for example, α-olefinscontaining from 3 to about 20, preferably from 3 to about 12, morepreferably from 3 to about 8 carbon atoms. Particularly suitable areethylene, propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1or ethylene in combination with one or more of propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1. These α-olefins do not containan aromatic moiety.

Other optional polymerizable ethylenically unsaturated monomer(s)include norbornene and C₁₋₁₀ alkyl or C₆₋₁₀ aryl substitutednorbornenes, with an exemplary interpolymer beingethylene/styrene/norbornene.

Suitable vinyl or vinylidene aromatic monomers, which can be employed toprepare the interpolymers, include, for example, those represented bythe following formula:

wherein R¹ is selected from the group of radicals consisting of hydrogenand alkyl radicals containing from 1 to about 4 carbon atoms, preferablyhydrogen or methyl; each R² is independently selected from the group ofradicals consisting of hydrogen and alkyl radicals containing from 1 toabout 4 carbon atoms, preferably hydrogen or methyl; Ar is a phenylgroup or a phenyl group substituted with from 1 to 5 substituentsselected from the group consisting of halo, C₁₋₄-alkyl, andC₁₋₄-haloalkyl; and n has a value from zero to about 4, preferably fromzero to 2, most preferably zero. Exemplary vinyl or vinylidene aromaticmonomers include styrene, vinyl toluene, (α-methylstyrene, t-butylstyrene, chlorostyrene, including all isomers of these compounds, andthe like. Particularly suitable such monomers include styrene and loweralkyl- or halogen-substituted derivatives thereof. Preferred monomersinclude styrene, α-methyl styrene, the lower alkyl-(C₁-C₄) orphenyl-ring substituted derivatives of styrene, such as for example,ortho-, meta-, and para-methylstyrene, the ring halogenated styrenes,para-vinyl toluene or mixtures thereof, and the like. A more preferredaromatic vinyl monomer is styrene.

By the term “sterically hindered aliphatic or cycloaliphatic vinyl orvinylidene compounds”, it is meant addition polymerizable vinyl orvinylidene monomers corresponding to the formula:

wherein A¹ is a sterically bulky, aliphatic or cycloaliphaticsubstituent of up to 20 carbons, R¹ is selected from the group ofradicals consisting of hydrogen and alkyl radicals containing from 1 toabout 4 carbon atoms, preferably hydrogen or methyl; each R² isindependently selected from the group of radicals consisting of hydrogenand alkyl radicals containing from 1 to about 4 carbon atoms, preferablyhydrogen or methyl; or alternatively R¹ and A¹ together form a ringsystem. Preferred aliphatic or cycloaliphatic vinyl or vinylidenecompounds are monomers in which one of the carbon atoms bearingethylenic unsaturation is tertiary or quaternary substituted. Examplesof such substituents include cyclic aliphatic groups such as cyclohexyl,cyclohexenyl, cyclooctenyl, or ring alkyl or aryl substitutedderivatives thereof, tert-butyl, norbornyl, and the like. Most preferredaliphatic or cycloaliphatic vinyl or vinylidene compounds are thevarious isomeric vinyl- ring substituted derivatives of cyclohexene andsubstituted cyclohexenes, and 5-ethylidene-2-norbornene. Especiallysuitable are 1-, 3-, and 4-vinylcyclohexene. Simple linear non-branchedα-olefins including for example, (α-olefins containing from 3 to about20 carbon atoms such as propylene, butene-1, 4-methyl-1-pentene,hexene-1 or octene-1 are not examples of sterically hindered aliphaticor cycloaliphatic vinyl or vinylidene compounds.

The substantially random interpolymers include the pseudo-randominterpolymers as described in EP-A-0,416,815 by James C. Stevens et al.and U.S. Pat. No. 5,703,187 by Francis J. Timmers, both of which areincorporated herein by reference in their entirety. The substantiallyrandom interpolymers also include the substantially random terpolymersas described in U.S. Pat. No. 5,872,201 which is also incorporatedherein by reference in its entirety. The substantially randominterpolymers are best prepared by polymerizing a mixture ofpolymerizable monomers in the presence of one or more metallocene orconstrained geometry catalysts in combination with various cocatalysts.Preferred operating conditions for the polymerization reactions arepressures from atmospheric up to 3000 atmospheres and temperatures from−30° C. to 200° C. Polymerizations and unreacted monomer removal attemperatures above the autopolymerization temperature of the respectivemonomers may result in formation of some amounts of homopolymerpolymerization products resulting from free radical polymerization.

Examples of suitable catalysts. and methods for preparing thesubstantially random interpolymers are disclosed in U.S. applicationSer. No. 702,475, filed May 20, 1991 (EP-A-514,828); as well as U.S.Pat. Nos. 5,055,438; 5,057,475; 5,096,867; 5,064,802; 5,132,380;5,189,192; 5,321,106; 5,347,024; 5,350,723; 5,374,696; 5,399,635;5,470,993; 5,703,187; and 5,721,185 all of which patents andapplications are incorporated herein by reference.

The substantially random α-olefin/vinyl aromatic interpolymers can alsobe prepared by the methods described in JP 07/278230 employing compoundsshown by the general formula

where Cp¹ and Cp² are cyclopentadienyl groups, indenyl groups, fluorenylgroups, or substituents of these, independently of each other; R¹ and R²are hydrogen atoms, halogen atoms, hydrocarbon groups with carbonnumbers of 1-12, alkoxyl groups, or aryloxyl groups, independently ofeach other; M is a group IV metal, preferably Zr or Hf, most preferablyZr; and R³ is an alkylene group or silanediyl group used to cross-linkCp¹ and Cp²).

The substantially random α-olefin/vinyl aromatic interpolymers can alsobe prepared by the methods described by John G. Bradfute et al. (W. R.Grace & Co.) in WO 95/32095; by R. B. Pannell (Exxon Chemical Patents,Inc.) in WO 94/00500; and in Plastics Technology, p. 25 (September1992), all of which are incorporated herein by reference in theirentirety.

Also suitable are the substantially random interpolymers which compriseat least one α-olefin/vinyl aromatic/vinyl aromatic/α-olefin tetraddisclosed in U.S. application Ser. No. 08/708,869 filed Sep. 4, 1996 andWO 98/09999 both by Francis J. Timmers et al. These interpolymerscontain additional signals in their carbon-13 NMR spectra withintensities greater than three times the peak to peak noise. Thesesignals appear in the chemical shift range 43.70-44.25 ppm and 38.0-38.5ppm. Specifically, major peaks are observed at 44.1, 43.9, and 38.2 ppm.A proton test NMR experiment indicates that the signals in the chemicalshift region 43.70-44.25 ppm are methine carbons and the signals in theregion 38.0-38.5 ppm are methylene carbons.

Further preparative methods for the interpolymers used in the presentinvention have been described in the literature. Longo and Grassi(Makromol. Chem., Volume 191, pages 2387 to 2396 [1990]) and D'Annielloet al. (Journal of Applied Polymer Science, Volume 58, pages 1701-1706[1995]) reported the use of a catalytic system based on methylalumoxane(MAO) and cyclopentadienyltitanium trichloride (CpTiCl₃) to prepare anethylene-styrene copolymer. Xu and Lin (Polymer Preprints, Am. Chem.Soc., Div. Polym. Chem.) Volume 35, pages 686,687 [1994]) have reportedcopolymerization using a MgCl₂/TiCl_(4/)NdCl₃/Al(iBu)₃ catalyst to giverandom copolymers of styrene and propylene. Lu et al (Journal of AppliedPolymer Science, Volume 53, pages 1453 to 1460 [1994]) have describedthe copolymerization of ethylene and styrene using aTiCl_(4/)NdCl₃/MgCl₂ /Al(Et)₃ catalyst. Sernetz and Mulhaupt, (Macromol.Chem. Phys., v. 197, pp. 1071-1083, 1997) have described the influenceof polymerization conditions on the copolymerization of styrene withethylene using Me₂Si(Me₄Cp)(N-tert-butyl)TiCl₂/methylaluminoxaneZiegler-Natta catalysts. Copolymers of ethylene and styrene produced bybridged metallocene catalysts have been described by Arai, Toshiaki andSuzuki (Polymer Preprints, Am. Chem. Soc., Div. Polym. Chem.) Volume 38,pages 349, 350 [1997]) and in U.S. Pat. No. 5,652,315, issued to MitsuiToatsu Chemicals, Inc. The manufacture of α-olefin/vinyl aromaticmonomer interpolymers such as propylene/styrene and butene/styrene aredescribed in U.S. Pat. No. 5,244,996, issued to Mitsui PetrochemicalIndustries Ltd or U.S. Pat. No. 5,652,315 also issued to MitsuiPetrochemical Industries Ltd or as disclosed in DE 197 11 339 A1 toDenki Kagaku Kogyo KK. All the above methods disclosed for preparing theinterpolymer component are incorporated herein by reference. Also,although of high isotacticity, the random copolymers of ethylene andstyrene as disclosed in Polymer Preprints Vol 39, No. 1, March 1998 byToru Aria et al. can also be employed as blend components for the foamsof the present invention.

While preparing the substantially random interpolymer, an amount ofatactic vinyl aromatic homopolymer may be formed due tohomopolymerization of the vinyl aromatic monomer at elevatedtemperatures. The presence of vinyl aromatic homopolymer is in generalnot detrimental for the purposes of the present invention and can betolerated. The vinyl aromatic homopolymer may be separated from theinterpolymer, if desired, by extraction techniques such as selectiveprecipitation from solution with a non solvent for either theinterpolymer or the vinyl aromatic homopolymer. For the purpose of thepresent invention it is preferred that no more than 30 weight percent,preferably less than 20 weight percent based on the total weight of theinterpolymers of atactic vinyl aromatic homopolymer is present.

The substantially random interpolymers comprise polymer units derivedfrom (1) about 0.5 to about 65 mole percent of either (a) at least onevinyl or vinylidene aromatic monomer, or (b) at least one hinderedaliphatic or cycloaliphatic vinyl or vinylidene monomer, or (c) acombination of at least one vinyl or vinylidene aromatic monomer and atleast one hindered aliphatic or cycloaliphatic vinyl or vinylidenemonomer; and (2) about 35 to about 99.5 mole percent of at least onealiphatic ax-olefin having from 2 to 20 carbon atoms.

The term “olefinic polymer” as used herein means olefinic polymerscomprising the aliphatic C₂-C₂₀ α-olefin homopolymers or interpolymers,or interpolymers of one or more aliphatic α-olefins and one or morenon-aromatic monomers interpolymerizable therewith (such as C₂-C₂₀α-olefins) or those aliphatic α-olefins having from 2 to 20 carbon atomsand containing polar groups. Suitable aliphatic α-olefin monomers whichintroduce polar groups into the polymer include, for example,ethylenically unsaturated nitriles such as acrylonitrile,methacrylonitrile, ethacrylonitrile, etc.; ethylenically unsaturatedanhydrides such as maleic anhydride; ethylenically unsaturated amidessuch as acrylamide, methacrylamide etc.; ethylenically unsaturatedcarboxylic acids (both mono- and difunctional) such as acrylic acid andmethacrylic acid, etc.; esters (especially lower, e.g. C₁-C₆, alkylesters) of ethylenically unsaturated carboxylic acids such as methylmethacrylate, ethyl acrylate, hydroxyethylacrylate, n-butyl acrylate ormethacrylate, 2-ethyl-hexylacrylate etc.; ethylenically unsaturateddicarboxylic acid imides such as N-alkyl or N-aryl maleimides such asN-phenyl maleimide, etc. Preferably such monomers containing polargroups are acrylic acid, vinyl acetate, maleic anhydride andacrylonitrile. Halogen groups which can be included in the polymers fromaliphatic α-olefin monomers include fluorine, chlorine and bromine;preferably such polymers are chlorinated polyethylenes (CPEs).

Preferred olefinic polymers for use in the present invention arehomopolymers or interpolymers of an aliphatic, including cycloaliphatic,alpha-olefin having from 2 to 18 carbon atoms. Suitable examples arehomopolymers of ethylene or propylene, and interpolymers of two or morealpha olefin monomers. Other preferred olefinic polymers areinterpolymers of ethylene and one or more other α-olefins having from 3to 8 carbon atoms. Preferred comonomers include 1-butene,4-methyl-1-pentene, 1-hexene, and 1-octene. The olefinic polymers mayalso contain, in addition to the alpha olefin, one or more non-aromaticmonomers interpolymerizable therewith. Such additionalinterpolymerizable monomers include, for example, C₄-C₂₀ dienes,preferably, butadiene or 5 ethylidene-2-norbornene.

The olefinic polymers can be further characterized by their degree oflong or short chain branching and the distribution thereof. One class ofolefinic polymers are the “branched ethylene homopolymers orinterpolymers” generally produced by a high pressure polymerizationprocess using a free radical initiator resulting in the traditional longchain branched low density polyethylene (LDPE). LDPE employed in thepresent composition usually has a density of less than 0.94 g/cc (ASTM D792). Also included in the family of branched homopolymers orinterpolymers are the ethylene-vinyl acetate copolymers (EVA), orethylene-acrylic acid copolymers (EAA).

Another class of olefinic polymers are the “linear ethylene homopolymersor interpolymers” which have an absence of long chain branching, andinclude the traditional linear low density polyethylene polymers(heterogeneous LLDPE) or linear high density polyethylene polymers(HDPE) made using Ziegler polymerization processes (for example, U.S.Pat. No. 4,076,698 (Anderson et al.), sometimes called heterogeneouspolymers.

Also included are the linear high density polyethylenes (HDPE) whichconsists mainly of long linear polyethylene chains. The HDPE employed inthe present invention usually has a density of at least 0.945 grams percubic centimeter (g/cc) as determined by ASTM D 792.

Another class of linear ethylene homopolymers or interpolymers isheterogeneous LLDPE, which when employed in the present inventiongenerally has a density of from 0.85 to 0.97 g/cc (ASTM D 792).Preferably the LLDPE is an interpolymer of ethylene and one or moreother (α-olefins having from 3 to 18 carbon atoms, more preferably from3-8 carbon atoms. Preferred comonomers include 1-butene,4-methyl-1-pentene, 1-hexene, and 1-octene.

A further class of linear ethylene homopolymers or interpolymers is thatof the uniformly branched or homogeneous polymers (e.g. homogeneouspolyethylene). The homogeneous polymers contain no long chain branchesand have only branches derived from the monomers (if having more thantwo carbon atoms). Homogeneous polymers include those made as describedin U.S. Pat. No. 3,645,992 (Elston), and those made using so-calledsingle site catalysts in a batch reactor having relatively high olefinconcentrations (as described in U.S. Pat. Nos. 5,026,798 and 5,055,438(Canich). The uniformly branched/homogeneous polymers are those polymersin which the comonomer is randomly distributed within a giveninterpolymer molecule and wherein the interpolymer molecules have asimilar ethylene/comonomer ratio within that interpolymer.

The homogeneous LLDPE employed in the present composition generally hasa density of from 0.85 to 0.94 g/cc (ASTM D 792). Preferably the LLDPEis an interpolymer of ethylene and one or more other (α-olefins havingfrom 3 to 18 carbon atoms, more preferably from 3-8 carbon atoms.Preferred comonomers include 1-butene, 4-methyl-1-pentene, 1-hexene, and1-octene.

Another class of olefinic polymers are the substantially linear ethylenehomopolymers or interpolymers. These polymers have a processabilitysimilar to LDPE, but the strength and toughness of LLDPE. Thesubstantially linear ethylene homopolymers or interpolymers aredisclosed in U.S. Pat. Nos. 5,272,236 and 5,278,272 which areincorporated herein by reference. The substantially linear ethylenehomopolymers or interpolymers can be a homopolymer of C₂-C₂₀ olefins,such as ethylene, propylene, 4-methyl-1-pentene, etc., or it can be aninterpolymer of ethylene with at least one C₃-C₂₀α-olefin and/or C₂-C₂₀acetylenically unsaturated monomer and/or C₄-C₁₈ diolefin. The polymercan also be an interpolymer of ethylene with at least one of the aboveC₃-C₂₀ α-olefins, diolefins and/or acetylenically unsaturated monomersin combination with other unsaturated monomers. The density of thesubstantially linear ethylene homopolymers or interpolymers as measuredin accordance with ASTM D-792 is generally from 0.85 g/cc to 0.97 g/cc,preferably from 0.85 g/cc to 0.955 g/cc, and especially from 0.85 g/ccto 0.92 g/cc.

Also included in the class of olefinic polymers are the ultra lowmolecular weight ethylene polymers and ethylene/α-olefin interpolymersdescribed in the U. S. patent application Ser. No. 784,683 entitledUltra-Low Molecular Weight Polymers, filed Jan. 22, 1997 M. J. Guest, etal., which is incorporated herein by reference. These ethylene/α-olefininterpolymers have I₂ melt indices greater than 1,000, or a numberaverage molecular weight (Mn) less than 11,000.

Also included in the class of olefinic polymers are the variouspolymeric ionomer compositions including Surlyn™ (a product andtrademark of Du Pont).

Especially preferred olefinic polymers comprise LDPE, HDPE,heterogeneous LLDPE, homogeneous linear polyethylene, substantiallylinear olefin polymer, polypropylene (PP), especially isotacticpolypropylene, syndiotactic polypropylene and rubber toughenedpolypropylenes, or ethylene-propylene interpolymers (EP), or chlorinatedpolyolefins (CPE), or ethylene-vinyl acetate copolymers (EVA), thepolymeric ionomer compositions or ethylene-acrylic acid copolymers, orany combination thereof.

The melt index, measured according to ASTM D-1238, Condition 190°C./2.16 kg (also known as I₂), of the polymer blend component(s) used inthe present invention is from about 0.01 to about 1000, preferably fromabout 0.01 g/10 min. to about 100, more preferably from about 0.1 toabout 50, and especially from about 0.1 to 10 g/10 min.

The term “coupling agent” or “grafting agent” as used hereininterchangeably means a compound or mixture of compounds used for thepurposes of coupling or grafting a polymer or polymer blend. Thecoupling agents used to prepare the grafted compositions of the presentinvention include, but are not limited to peroxides, silanes, radiation,azides, phenols (as disclosed in U.S. Pat. No. 4,311,628, the disclosureof which is incorporated herein by reference), aldehyde-amine reactionproducts (including formaldehyde-ammonia;formaldehyde-ethylchloride-ammonia; acetaldehyde-ammonia;formaldehyde-aniline; butyraldehyde-aniline; and heptaldehyde-aniline),substituted ureas (include trimethylthiourea; diethylthiourea;dibutylthiourea; tripentylthiourea;1,3-bis(2-benzothiazolylmercaptomethyl)urea; and N,N-diphenylthiourea),substituted guanidines (including diphenylguanidine;di-o-tolylguanidine; diphenylguanidine phthalate; and thedi-o-tolylguanidine salt of dicatechol borate); substituted xanthates(including zinc ethylxanthate; sodium isopropylxanthate; butylxanthicdisulfide; potassium isopropylxanthate; and zinc butylxanthate);substituted dithiocarbamates (including copper dimethyl-, zincdimethyl-, tellurium diethyl-, cadmium dicyclohexyl-, lead dimethyl-,lead dimethyl-, selenium dibutyl-, zinc pentamethylene-, zinc didecyl-,and zinc isopropyloctyl-dithiocarbamate); sulfur-containing compounds,such as thiazoles (including 2-mercaptobenzothiazole, zincmercaptothiazolyl mercaptide, 2-benzothiazolyl-N,N-diethylthiocarbamylsulfide, and 2,2′-dithiobis(benzothiazole), imidazoles (including2-mercaptoimidazoline and 2-mercapto-4,4,6-trimethyldihydropyrimidine),sulfenamides (including N-t-butyl-2-benzothiazole-,N-cyclohexylbenzothiazole-, N,N-diisopropylbenzothiazole-,N-(2,6-dimethylmorpholino)-2-benzothiazole-, andN,N-diethylbenzothiazole-sulfenamide)thiuramidisulfides (includingN,N′-diethyl-, tetrabutyl-, N,N′-diisopropyldioctyl-, tetramethyl-,N,N′-dicyclohexyl-, and N,N′-tetralauryl-thiuramidisulfide),paraquinonedioxime, dibenzoparaquinonedioxime, sulfur; and combinationsthereof. See Encyclopedia of Chemical Technology, Vol. 17, 2nd edition,Interscience Publishers, 1968; also Organic Peroxides, Daniel Seem, Vol.1, Wiley-Interscience, 1970).

The various coupling technologies are described in U.S. Pat. Nos.5,869,591 and 5,977,271, the entire contents of both of which are hereinincorporated by reference. Dual cure systems, which use a combination ofheat, moisture cure, and radiation steps, may be effectively employed.Dual cure systems are disclosed and claimed in U.S. Pat. No. 6,124,370,incorporated herein by reference. For instance, it may be desirable toemploy peroxide coupling agents in conjunction with silane couplingagents, peroxide coupling agents in conjunction with radiation,sulfur-containing coupling agents in conjunction with silane couplingagents, etc.

Suitable peroxides include aromatic diacyl peroxides; aliphatic diacylperoxides; dibasic acid peroxides; ketone peroxides; alkyl peroxyesters;alkyl hydroperoxides (for example, diacetylperoxide; dibenzoylperoxide;bis-2,4-dichlorobenzoyl peroxide; di-tert-butyl peroxide;dicumylperoxide; tert-butylperbenzoate; tert-butylcumylperoxide; 2,5-bis(t-butylperoxy)-2,5-dimethylhexane; 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne-3;4,4,4′,4′-tetra-(t-butylperoxy)-2,2-dicyclohexylpropane;1,4-bis-(t-butylperoxyisopropyl)-benzene;1,1-bis-(t-butylperoxy)-3,3,5-trimethylcyclohexane; lauroyl peroxide;succinic acid peroxide; cyclohexanone peroxide; t-butyl peracetate;butyl hydroperoxide; etc. Preferred are2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3 and2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, the former is available asLupersol™ 130 and the latter as Lupersol™ 101, both trademarks andproducts of Elf Atochem.

Suitable azide coupling agents include azidoformates, such astetramethylenebis(azido-formate) (see, also, U.S. Pat. No. 3,284,421,Breslow, Nov. 8, 1966); aromatic polyazides, such as4,4′-diphenylmethane diazide (see, also, U.S. Pat. No. 3,297,674,Breslow et al., Jan. 10, 1967); and the poly(sulfonyl azides), such asp,p′-oxybis-(benzene sulfonyl azide).

The poly(sulfonyl azides) are any compounds having at least two sulfonylazide. groups (—SO₂N₃) reactive with the polymer(s). Preferably thepoly(sulfonyl azide)s have a structure X—R—X wherein each X is SO₂N₃ andR represents an unsubstituted or inertly substituted hydrocarbyl,hydrocarbyl ether or silicon-containing group, preferably havingsufficient carbon, oxygen or silicon, preferably carbon, atoms toseparate the sulfonyl azide groups sufficiently to permit a facilereaction between the polymer(s) and the sulfonyl azide, more preferablyat least 1, more preferably at least 2, most preferably at least 3carbon, oxygen or silicon, preferably carbon, atoms between functionalgroups. While there is no critical limit to the length of R, each Radvantageously has at least one carbon or silicon atom between X's andpreferably has less than about 50, more preferably less than about 30,most preferably less than about 20 carbon, oxygen or silicon atoms.Within these limits, larger is better for reasons including thermal andshock stability. When R is straight-chain alkyl hydrocarbon, there arepreferably less than 4 carbon atoms between the sulfonyl azide groups toreduce the propensity of the nitrene to bend back and react with itself.Silicon containing groups include silanes and siloxanes, preferablysiloxanes. The term inertly substituted refers to substitution withatoms or groups which do not undesirably interfere with the desiredreaction(s) or desired properties of the resulting coupled polymers.Such groups include fluorine, aliphatic or aromatic ether, siloxane aswell as sulfonyl azide groups when more than two polyolefin chains areto be joined. Suitable structures include R as aryl, alkyl, arylalkaryl, arylalkyl silane, siloxane or heterocyclic, groups and othergroups which are inert and separate the sulfonyl azide groups asdescribed. More preferably R includes at least one aryl group betweenthe sulfonyl groups, most preferably at least two aryl groups (such aswhen R is 4,4′ diphenylether or 4,4′-biphenyl). When R is one arylgroup, it is preferred that the group have more than one ring, as in thecase of naphthylene bis(sulfonyl azides). Poly(sulfonyl)azides includesuch compounds as 1, 5-pentane bis(sulfonlazide), 1,8-octanebis(sulfonyl azide), 1,10-decane bis(sulfonyl azide), 1,10-octadecanebis(sulfonyl azide), 1-octyl-2,4,6-benzene tris(sulfonyl azide),4,4′-diphenyl ether bis(sulfonyl azide),1,6-bis(4′-sulfonazidophenyl)hexane, 2,7-naphthalene bis(sulfonylazide), and mixed sulfonyl azides of chlorinated aliphatic hydrocarbonscontaining an average of from 1 to 8 chlorine atoms and from about 2 to5 sulfonyl azide groups per molecule, and mixtures thereof. Preferredpoly(sulfonyl azide)s include oxy-bis(4-sulfonylazidobenzene),2,7-naphthalene bis(sulfonyl azido), 4,4′-bis(sulfonyl azido)biphenyl,4,4′-diphenyl ether bis(sulfonyl azide) and bis(4-sulfonylazidophenyl)methane, and mixtures thereof.

Sulfonyl azides are conveniently prepared by the reaction of sodiumazide with the corresponding sulfonyl chloride, although oxidation ofsulfonyl hydazines with various reagents (nitrous acid, dinitrogentetroxide, nitrosonium tetrafluoroborate) has also been used.

Polyfunctional compounds capable of insertions into C—H bonds alsoinclude carbene-forming compounds such as salts of alkyl and arylhydrazones and diazo compounds, and nitrene-forming compounds such asalkyl and aryl azides (R—N₃), acyl azides (R—C(O)—N₃), azidoformates(R—O—C(O)—N₃), sulfonyl azides (R—SO₂—N₃), phosphoryl azides((RO)₂—(PO)—N₃), phosphinic azides (R₂—P(O)—N₃)and silyl azides(R₃—Si—N₃).

Alternatively, silane coupling agents may be employed. In this regard,any silane that will effectively graft the polymers of this inventioncan be used. Suitable silanes include unsaturated silanes that comprisean ethylenically unsaturated hydrocarbyl group, such as a vinyl, allyl,isopropenyl, butenyl, cyclohexenyl or γ-(meth)acryloxy allyl group, anda hydrolyzable group, such as, for example, a hydrocarbyloxy,hydrocarbonyloxy, or hydrocarbylamino group. Examples of hydrolyzablegroups include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, andalkyl or arylamino groups. Preferred silanes are the unsaturated alkoxysilanes which can be grafted onto the polymer. These silanes and theirmethod of preparation are more fully described in U.S. Pat. No.5,266,627 to Meverden, et al. Vinyl trimethoxy silane (VTMOS), vinyltriethoxy silane, γ-(meth)acryloxy propyl trimethoxy silane and mixturesof these silanes are the preferred silane coupling agents for use inthis invention.

The amount of silane coupling agent used in the practice of thisinvention can vary widely depending upon the nature of the substantiallyrandom interpolymer, the silane employed, the processing conditions, theamount of grafting initiator, the ultimate application, and similarfactors.

The silane coupling agent is used to graft the polymers of thisinvention by any conventional method, typically in the presence of afree radical initiator for example peroxides and azo compounds, or byionizing radiation, etc. Organic initiators are preferred, such as anyone of the peroxide initiators, for example, dicumyl peroxide,di-tert-butyl peroxide, t-butyl perbenzoate, benzoyl peroxide, cumenehydroperoxide, t-butyl peroctoate, methyl ethyl ketone peroxide,2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, lauryl peroxide, andtert-butyl peracetate. A suitable azo compound is azobisisobutylnitrite.

Those skilled in the art will be readily able to select amounts ofinitiator employed, with the amount selected taking into accountcharacteristics of the polymers, such as molecular weight, molecularweight distribution, comonomer content, as well as the presence ofcoupling enhancing coagents, additives (such as oil) etc. Typically, theamount of initiator employed will not exceed that which is required toeffect grafting.

While any conventional method can be used to silane graft the polymers,one preferred method is blending the two with the initiator in the firststage of a reactor extruder, such as a Buss kneader. The graftingconditions can vary, but the melt temperatures are typically between160° C. and 260° C., preferably between 190° C. and 230° C., dependingupon the residence time and the half-life of the initiator.

Cure is promoted with a coupling catalyst, and any catalyst that willprovide this function can be used in this invention. These catalystsgenerally include organic bases, carboxylic acids, and organometalliccompounds including organic titanates and complexes or carboxylates oflead, cobalt, iron, nickel, zinc and tin. Dibutyltindilaurate,dioctyltinmaleate, dibutyltindiacetate, dibutyltindioctoate, stannousacetate, stannous octoate, lead naphthenate, zinc caprylate, cobaltnaphthenate. Tin carboxylate, especially dibutyltindilaurate anddioctyltinmaleate, are particularly effective for this invention.

Rather than employing a chemical coupling agent, coupling may beeffected by use of radiation. Useful radiation types include electronbeam or beta ray, gamma rays, X-rays, or neutron rays. Radiation isbelieved to effect coupling by generating polymer radicals which maycombine and crosslink. Additional teachings concerning radiationcoupling are seen in C. P. Park, “Polyolefin Foam” Chapter 9, Handbookof Polymer Foams and Technology, D. Klempner and K. C. Frisch, eds.,Hanser Publishers, New York (1991), pages 198-204, which is incorporatedherein by reference.

Radiation dosage depends upon the blend polymer compositions. Thoseskilled in the art will be readily able to select suitable radiationlevels, taking into account such variables as thickness and geometry ofthe article to be irradiated, as well as to characteristics of thepolymers, such as molecular weight, molecular weight distribution,comonomer content, the presence of coupling enhancing coagents,additives (such as oil), etc. Typically, the dosage will not exceed thatwhich is required to effect the desired level of coupling.

The choice of coupling agent will depend on the types of polymers beinggrafted. The coupling agent may be added in a variety of ways. Forinstance, powder or liquid or pellets may be added to and/or tumbleblended with one or more of the blend polymer components which havepreferably (but not necessarily) been surface treated with tackifiers.Tackifiers can be obtained by the polymerization of petroleum andterpene feedstreams and from the derivatization of wood, gum, and talloil rosin. Several classes of tackifiers include wood rosin, tall oiland tall oil derivatives, and cyclopentadiene derivatives, such as aredescribed in United Kingdom patent application GB 2,032,439A. Otherclasses of tackifiers include aliphatic C₅ resins, polyterpene resins,hydrogenated resins, mixed aliphatic-aromatic resins, rosin esters,natural and synthetic terpenes, terpene-phenolics, and hydrogenatedrosin esters. A preferred tackifier is mineral oil.

Alternatively, the coupling agent is dispersed in a suitablenon-reactive liquid or tackifier (such as mineral oil) which is thentumble blended with one or more of the blend polymer components. It isespecially preferred that the oil is of a room temperature viscositysuch that it has sufficient flow to completely wet the surface of thepellets, and yet be sufficiently viscous such it does not drain quicklyon standing prior to feeding to the extruder. A preferred oil is thewhite mineral oil, Drakeol™ 34 (a registered trademark and product ofThe Pennzoil Company). The dispersion of coupling agent in non-reactiveliquid may also be injected into a melt processing equipment (such as anextruder) used to make the grafted blend compositions.

The amount of non-reactive liquid or tackifier (such as mineral oil)used will vary, and typically is in the range of 0.2-2.0 wt % (but thisis not limiting). Alternatively, the coupling agent may first becompounded in a suitable thermoplastic polymer and pellets, etc of thecompound may then be tumble blended with the other blend componentsbefore reactive extrusion or independently fed to the extruder.

Those skilled in the art will be readily able to select amounts ofcoupling agent, with the amount selected taking into accountcharacteristics of the polymer(s) such as molecular weight, molecularweight distribution, comonomer content, the presence of couplingenhancing coagents, additives (such as oil) etc. Since it is expresslycontemplated that the polymer(s) may be blended prior to coupling, thoseskilled in the art may use the following guidelines as a reference pointin optimizing the amount of coupling agent preferred for the particularblends in question. Typically, the amount of coupling agent employedwill not exceed that which is required to effect the desired level ofcoupling.

To graft, the coupling agent is used in an amount effective to result inthe formation of 50 percent or less, preferably 40 percent or less, morepreferably 30 percent or less, even more preferably 20 percent or less,most preferably 10 percent or less weight percent gel as evidenced byinsolubility of the gels in boiling xylene when tested according to ASTMD-2765A-84. This amount may vary depending on the type of the couplingagent, but is generally less than about 2.0, preferably less than about1.0, more preferably less than about 0.5, most preferably less thanabout 0.2 weight percent coupling agent (based on the, total weight ofcoupling agent and polymer blend components), with these valuesdepending on the molecular weight of the coupling agent and themolecular weight or melt index of polymers.

The coupling agent and blend are mixed at a first temperature which isat least the melting point of the lowest melting component of the blendand, after mixing, are heated to react at a second temperature which isat least greater than the first temperature and is usually greater than100° C. and most frequently greater than 150° C. The preferredtemperature range depends on the nature of the coupling agent that isused. For example, in the case of azides (including but not limited to4,4′-disulfonylazidediphenylether) and peroxides (including but notlimited to 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne-3), the preferredtemperature range is greater than 150° C., preferably greater than 160°C., more preferably greater than 185° C., most preferably greater than190° C. Preferably, the upper temperature is less than 300° C.

Temperatures for use in the practice of the invention are alsodetermined by the softening or melt temperatures of the polymer startingmaterials. For these reasons, the temperature is advantageously greaterthan about 90° C., preferably greater than about 120° C., morepreferably greater than about 150° C., and most preferably greater than170° C.

We have also surprisingly found that further improvements in meltstrength of the coupled blends may be achieved by reacting attemperatures greater than or equal to 240° C., more preferably greaterthan or equal to 250° C. even more preferably greater than or equal to260° C.

Preferred times at the desired decomposition temperatures are times thatare sufficient to result in complete reaction of the coupling agent withthe polymer(s). Preferred reaction times in terms of the half-life ofthe coupling agent (that is the time required for about half of theagent to be reacted at a preselected temperature, and determinable byDSC) is about 5 half-lives of the coupling agent. In the case of abis(sulfonyl azide), for instance, the reaction time is preferably atleast about 4 minutes at 200° C.

Admixing of the polymer and coupling agent is conveniently accomplishedby any means within the skill in the art. Desired distribution isdifferent in many cases, depending on what properties are to bemodified. In a blend it is often desirable to have low solubility in oneor more of the polymer matrices such that the coupling agent ispreferentially in the other phase, or predominantly in the interfacialregion between the two phases.

Treatment of blends with the coupling agent according to practice of theinvention results in blends of the invention, which are referred toherein as grafted blends. A blend is advantageously mixed with acoupling agent above the softening temperature of at least one componentof the blend, most preferably below the peak decomposition temperatureof the coupling agent, and the resulting mixture is preferably raised toat least the peak decomposition temperature of the coupling agent.

Practice of the invention advantageously involves forming asubstantially uniform admixture of polymers and coupling agent (beforeits decomposition). In the case of blends where there are dispersed andcontinuous phases, it may be sufficient for the coupling agent to bedispersed at the interface of the phases rather than being uniformlydistributed.

Processes for coupling include at least one of (a) dry blending thecoupling agent with the polymer, preferably to form a substantiallyuniform admixture and adding this mixture to melt processing equipment,e.g. a melt extruder to achieve the coupling reaction, at a temperatureat least the decomposition temperature of the coupling agent; (b)introducing, e.g. by injection, a coupling agent in liquid form, e.g.dissolved in a solvent therefor or in a slurry of coupling agent in aliquid, into a device containing polymer, preferably softened, molten ormelted polymer, but alternatively in particulate form, in solution ordispersion, more preferably in melt processing equipment; (c) forming afirst admixture of a first amount of a first polymer and a couplingagent, advantageously at a temperature less than about the decompositiontemperature of the coupling agent, preferably by melt blending, and thenforming a second admixture of the first admixture with a second amountof a second polymer (for example a concentrate of a coupling agentadmixed with at least one polymer and optionally other additives, isconveniently admixed into a second polymer or combination thereofoptionally with other additives, to modify the second polymer(s)); (d)feeding at least one coupling agent, preferably in solid form, morepreferably finely comminuted, e.g. powder, directly into softened ormolten polymer, e.g. in melt processing equipment, e.g. in an extruder;or combinations thereof.

Process (c) is conveniently used to make a concentrate with a firstpolymer composition having a lower melting temperature, advantageouslyat a temperature below the decomposition temperature of the couplingagent, and the concentrate is melt blended into a second polymercomposition having a higher melting temperature to complete the couplingreaction.

Concentrates are especially preferred when temperatures are sufficientlyhigh to result in loss of coupling agent by evaporation or decompositionnot leading to reaction with the polymer, or other conditions wouldresult that effect. Alternatively, some coupling occurs during theblending of the first polymer and coupling agent, but some of thecoupling agent remains unreacted until the concentrate is blended intothe second polymer composition. The polymer composition optionallyincludes additives known within the skill in the art. When the couplingagent is added in a dry form it is preferred to mix the agent andpolymer in a softened or molten state below the decompositiontemperature of the coupling agent then to heat the resulting admixtureto a temperature at least equal to the decomposition temperature of thecoupling agent.

The polyolefin(s) and coupling agent are suitably combined in any mannerwhich results in desired reaction thereof, preferably by mixing thecoupling agent with the polymer(s) under conditions which allowsufficient mixing before reaction to avoid uneven amounts of localizedreaction then subjecting the resulting admixture to heat sufficient forreaction. Preferably, a substantially uniform admixture of couplingagent and polymer is formed before exposure to conditions in which chaincoupling takes place.

A substantially uniform admixture is one in which the distribution ofcoupling agent in the polymer is sufficiently homogeneous to beevidenced by a polymer having a melt viscosity after treatment accordingto the practice of the invention either higher at low angular frequency(e.g. 0.1 rad/sec) or lower at higher angular frequency (e.g. 100rad/sec) than that of the same polymer which has not been treated withthe coupling agent but has been subjected to the same shear and thermalhistory.

Thus, preferably, in the practice of the invention, decomposition of thecoupling agent occurs after mixing sufficient to result in asubstantially uniform admixture of coupling agent and polymer. Thismixing is preferably attained with the polymer in a molten or meltedstate, which is above the crystalline melt temperature, or in adissolved or finely dispersed condition rather than in a solid mass orparticulate form. The molten or melted form is more preferred to insurehomogeneity rather than localized concentrations at the surface.

While any equipment can be suitably used, equipment which providessufficient mixing and temperature control in the same equipment,including such devices as an extruder, or a static polymer mixing devisesuch as a Brabender blender, are preferred. The term extruder is used inits broadest meaning to include such devices as those, which extrudepellets such as a pelletizer.

In one embodiment of the invention, the grafting process takes place ina single vessel, that is mixing of the coupling agent and polymer takesplace in the same vessel as heating to the decomposition temperature ofthe coupling agent. The vessel is preferably an extruder, which mayoptionally be suitable for foam preparation. The reaction vessel morepreferably has at least two zones of different temperatures into which areaction mixture passes. The first zone advantageously is at atemperature of at least the crystalline melt temperature or thesoftening temperature of the polymer(s) and preferably less than thedecomposition temperature of the coupling agents, with the second zonebeing at a temperature sufficient for decomposition of the couplingagent. The first zone is preferably at a temperature sufficiently highto soften the polymer and allow it to combine with the coupling agent,through distributive mixing to a substantially uniform admixture.Addition of a blowing agent may optionally occur in either of thesezones, depending on the temperatures advantageous for its use.

In one embodiment the foam forming step or steps and the grafting stepsare at least partially simultaneous. Thus the coupling agent isintroduced during any step before or in a foam forming process that isof a temperature sufficiently low to result in adequate mixing before orduring grafting and grafting takes place in or simultaneous with anystep in a foam forming process in which the temperature is at leastabout the decomposition temperature of the coupling agent. Grafting,however, preferably takes place before the foam is extruded or otherwiseexits the vessel in which the polymer is admixed with any blowing agent.

For polymers that have softening points above the coupling agentdecomposition temperature (preferably greater than 200° C.), andespecially when incorporation of a lower melting polymer (such as in aconcentrate) is undesirable, the preferred method for incorporation ofcoupling agent is to solution blend the coupling agent in solution oradmixture into the polymer, (this allows the polymer to imbibe i.e.absorb or adsorb at least some of the coupling agent), and then toevaporate the solvent. After evaporation, the resulting mixture isextruded. The solvent is preferably a solvent for the coupling agent,and more preferably also for the polymer when the polymer is solublesuch as in the case of polycarbonate. Such solvents include polarsolvents such as acetone, THF (tetrahydrofuran) and chlorinatedhydrocarbons such as methylene chloride. Alternatively other non-polarcompounds such as mineral oils in which the coupling agent issufficiently miscible to disperse the coupling agent in a polymer, areused.

The present invention can be summarized in terms of the followingembodiments:

Embodiment One

In one embodiment of the present invention, it has been found that themelt strength, hardness and/or upper service temperature of certainblend compositions comprising, (A) one or more homopolymers orinterpolymers with peak crystalline melting temperature (Tm) and/orglass transition temperature (Tg by DSC) of 90° C. or more; (B) one ormore homopolymers or interpolymers with peak crystalline meltingtemperature (Tm) and/or glass transition temperature (Tg by DSC) of 80°C. or less; can be increased significantly by grafting with (C) at leastone coupling agent, preferably an azide or peroxide.

These blends of Embodiment One can comprise a grafted blend of

1) two or more substantially random interpolymers;

2) two or more olefinic polymers;

3) two or more alkenyl aromatic polymers

4) one or more substantially random interpolymers and one or moreolefinic polymers;

5) one or more substantially random interpolymers, and one or morealkenyl aromatic polymers; or

6) one or more olefinic polymers, and one or more alkenyl aromaticpolymers; or

7) one or more substantially random interpolymers, and one or morealkenyl aromatic polymers; or

8) one or more olefinic polymers, one or more substantially randominterpolymers and one or more alkenyl aromatic polymers.

The resulting blends exhibit a more than additive increase in meltstrength. This improvement is believed to result from the coupling agentreacting with more than one polymer chain to connect them, referred toherein as “grafting”. Grafting results in rheology modification, i.e.,change in melt viscosity of a polymer as determined by dynamicmechanical spectroscopy. The blends of Embodiment One advantageouslyhave increased melt strength and are thus useful in making fibers, filmand foams.

The blends of this invention will have upper service temperature greaterthan 80° C., preferably greater than 85° C. and most preferably greaterthan 90° C.

The blends will comprise: (A) from about 0.5 to about 99.5, preferablyfrom about 5 to about 95, more preferably from about 10 to about 90,most preferably from about 10 to about 60 weight percent (based on thecombined weights of components A and B) of one or more homopolymers orinterpolymers with peak crystalline melting temperature (Tm) and/orglass transition temperature (Tg by DSC) of 90° C. or more; and (B) fromabout 0.5 to about 99.5, preferably from about 5 to about 95, morepreferably from about 10 to about 90, most preferably from about 40 toabout 90 weight percent (based on the combined weights of components Aand B) of one or more homopolymers or interpolymers with peakcrystalline melting temperature (Tm) and/or glass transition temperature(Tg by DSC) of 80° C. or less; and (C) one or more coupling agents.

The resulting grafted blend has (1) a gel content which is 50 percent orless, preferably 40 percent or less, more preferably 30 percent or less,even more preferably 20 percent or less, most preferably 10 percent orless as determined by insolubility of the gels in boiling xylene whentested according to ASTM D-2765A-84, (2) an increase in melt strength of5% or more, preferably 10 percent or more relative to the same polymerblend without the coupling agent; and (3) an increase in upper servicetemperature (as measured by Thermal Mechanical Analyses (TMA)) of 0.5°C. or more, preferably 1.0° C. or more, more preferably 1.5° C. or more,even more preferably 5° C. or more relative to the same polymer blendwithout the coupling agent.

The resulting grafted blend also has a melt elongation greater than orequal to about 20 mm/s, preferably greater than or equal to about 25mm/s, more preferably greater than or equal to about 30 mm/s.

Embodiment Two

We have also surprisingly found grafted blend compositions that exhibita unique combination of high melt strength, high melt elongation andhigh flexural modulus.

The final grafted blend compositions comprise either; (A) one or morelinear or substantially linear ethylene homopolymers or interpolymersand one or more branched ethylene homopolymers or interpolymers; or (B)one or more linear or substantially linear ethylene homopolymers orinterpolymers and one or more substantially random interpolymers; or (C)one or more linear or substantially linear ethylene homopolymers orinterpolymers, one or more branched ethylene homopolymers orinterpolymers and one or more substantially random interpolymers; all ofwhich blends are grafted with (D) one or more coupling agents.

The final grafted blend compositions exhibit high melt strength, that isvalues greater than about 8, preferably greater than about 10, morepreferably greater than about 15 cN.

The final grafted blend compositions also have high melt elongation,that is values of 20 mm/s or greater, preferably 25 mm/s or greater.

The final grafted blend compositions also have high flexural modulus,that is values of 80,000 psi or greater, preferably 100,000 psi orgreater, most preferably 110,000 psi or greater.

The final grafted blend compositions also have a gel content which is 50percent or less, preferably 40 percent or less, more preferably 30percent or less, even more preferably 20 percent or less, mostpreferably 10 percent or less as determined by insolubility of the gelsin boiling xylene when tested according to ASTM D-2765A-84.

Even more preferably, the gel content of the present grafted blendcomposition is 10 or less, preferably 5 or less, more preferably 2 orless weight percent gel as evidenced by insolubility of the gels inboiling xylene when tested according to ASTM D-2765A-84.

Preferably these compositions comprise a grafted blend of heterogeneousor homogeneous LLDPE with LDPE, or HDPE with LDPE, or a substantiallylinear ethylene homopolymer or interpolymer with LDPE.

The coupling agent is preferably an azide or peroxide or combinationthereof.

Embodiment Three

In another embodiment of the present invention, it has been surprisinglyfound that certain grafted blend compositions comprising polypropyleneare able to exhibit high melt strength while retaining acceptably highflexural modulus (50,000 psi or greater).

The grafted blend compositions comprise (A) one or more olefinicpolymers other than polypropylene; (B) one or more propylenehomopolymers or interpolymers; and (C) at least one coupling agent,preferably an azide or peroxide.

The resulting grafted blend composition has a gel content which is 50percent or less, preferably 40 percent or less, more preferably 30percent or less, even more preferably 20 percent or less, mostpreferably 10 percent or less as determined by insolubility of the gelsin boiling xylene when tested according to ASTM D-2765A-84.

The resulting grafted blend composition has a melt strength greater thanabout 5, preferably greater than about 10, more preferably greater thanabout 15 cN.

The resulting grafted blend also has a melt elongation greater than orequal to about 20 mm/s, preferably greater than or equal to about 25mm/s.

The resulting grafted blend composition has a flexural modulus of 50,000psi or greater.

Blends and Fabricated Articles Made from the Grafted Blends ofEmbodiments One to Three

The present invention also includes blends and any fabricated article,which comprise any of the grafted blends of Embodiments One to Three.The blends and fabricated articles will comprise 0.05 to 100, preferably0.1 to 100 and most preferably 0.2 to 100 weight percent of the graftedblends of Embodiments 1-3 (based on total amount of polymers present inthe final blend or fabricated article).

The grafted blends of the various embodiments of the present inventionmay be advantageously used to produce a wide range of fabricatedarticles including foams, calendared, cast and blown sheets and films,compression and injection molded parts, rotational molded parts, fibersand the like. The blends are also useful in applications such asmodifiers for bitumen and asphalt compositions, as components for hotmelt and pressure sensitive adhesive systems, extrusion coating,blowmolding, high speed fiber spinning, oriented nonwovens,thermoforming, labels, candy wrappers, geomembranes, cereal liners, wireand cable, pipes, etc. Preferably the article is formed from a melt ofthe composition. More preferably it is formed by a melt process.

Blending the grafted blends of the aforementioned Embodiments 1-3 withone or more other thermoplastics provides additional improvements inproperties including but not limited to upper service temperature,modulus, compressive strength, hardness, toughness, increased foam cellsize, and aesthetics of the final fabricated articles (depending on ifthe graft or other thermoplastic is the predominant blend component).

Examples of the other thermoplastic include, but are not limited to,ethylene styrene interpolymers (ESI), ethylene vinylacetate copolymers(EVA), polypropylene (PP), polystyrene (PS), high density polyethylene(HDPE), low density polyethylene (LDPE), and linear low densitypolyethylene (LLDPE). In one embodiment, grafted blends of theaforementioned Embodiments 1-3, may be further blended with alkenylaromatic polymers (such as polystyrene) to make, for example, alkenylaromatic polymer foams with increased cell size.

The grafted blends or their blends with other thermoplastics may beprepared by any suitable means known in the art such as, for example,dry blending in a pelletized form in desired proportions followed bymelt blending in an apparatus such as a screw extruder or a Banburymixer. Dry blended pellets may be directly melt processed into a finalsolid state article by, for example, injection molding. The blends mayalso be made by direct polymerization without isolating blendcomponents. Direct polymerization may use, for example, one or morecatalysts in a single reactor or two or more reactors in series orparallel and vary at least one of operating conditions, monomer mixturesand catalyst choice.

Various additives may optionally be incorporated into the blendcompositions or fabricated articles of the present invention. Theadditives include, without limitation, stability control agents(specifically for foams), nucleating agents (specifically for foams),inorganic fillers, conductive fillers, pigments, colorants,antioxidants, acid scavengers, ultraviolet absorbers or stabilizers,flame retardants, processing aids, extrusion aids, anti-static agents,cling additives (e.g., polyiso-butylene), antiblock additives, otherthermoplastic polymers, and the like. Certain of the additives, such asinorganic and conductive fillers, may also function as nucleating agentsand/or open cell promoters for foams. Examples of antioxidants arehindered phenols (such as, for example, Irganox™ 1010) and phosphites(e.g., Irgafos™ 168) both trademarks of, and commercially availablefrom, Ciba Geigy Corporation.

The additives are advantageously employed in functionally equivalentamounts known to those skilled in the art. For example, the amount ofantioxidant employed is that amount which prevents the polymer orpolymer blend from undergoing oxidation at the temperatures andenvironment employed during storage and ultimate use of the polymers.Such amount of antioxidants is usually in the range of from 0.01 to 10,preferably from 0.02 to 5, more preferably from 0.03 to 2 percent byweight based upon the weight of the polymer or polymer blend. Similarly,the amounts of any of the other enumerated additives are thefunctionally equivalent amounts such as the amount to render the polymeror polymer blend antiblocking, the desired amount of filler loading toproduce the desired result, to provide the desired color from thecolorant or pigment. Such additives are advantageously employed in therange of from 0.01 to 90, preferably from 0.02 to 70, more preferablyfrom 0.05 to 50 percent by weight based upon the weight of the polymeror polymer blend.

In the case of foams, a nucleating agent is optionally added in order tocontrol the size of foam cells. Preferred nucleating agents includeinorganic substances such as calcium carbonate, talc, clay, titaniumoxide, silica, barium stearate, barium sulfate, diatomaceous earth,mixtures of citric acid and sodium bicarbonate, and the like. When used,the amount of nucleating agent employed may range from >0 to about 5parts by weight per hundred parts by weight of polymer (phr).

In the case of foams, a stability control agent (also known aspermeability modifier) is optionally added to the present foam toenhance dimensional stability. Preferred agents include amides andesters of C₁₀₋₂₄ fatty acids. Such agents are seen in U.S. Pat. Nos.3,644,230 and 4,214,054, which are incorporated herein by reference.Esters may also reduce static during and after foam manufacture. Mostpreferred agents include stearyl stearamide, glyceromonostearate,glycerol monobehenate, and sorbitol monostearate. When used, suchstability control agents are typically employed in an amount rangingfrom >0 to about 10 parts per hundred parts of the polymer.

The blend compositions or fabricated articles made from the graftedblends of this invention may be substantially free of crosslinking(i.e., contain 50 percent or less, preferably 40 percent or less, morepreferably 30 percent or less, even more preferably 20 percent or less,most preferably 10 percent or less weight percent gel based upon totalweight of polymer, as measured according to ASTM D-2765-84, Method A).

Alternatively, the grafted blend compositions could be used to makeblends or or fabricated articles which are substantially cross-linked(i.e., contain greater than 45 weight percent gel based upon the totalweight of polymer, as measured according to ASTM D-2765-84 Method A) byfurther addition of any known cross-linking agent.

The term “cross-linking agent” as used herein means a compound ormixture of compounds used for the purposes of substantially crosslinkinga polymer or polymer blend. The cross-linking agent used to prepare thecompositions and articles of the present invention include, but are notlimited to peroxides, silanes, radiation, azides, phenols,aldehyde-amine reaction products, substituted ureas, substitutedguanidines, substituted xanthates, substituted dithiocarbamates,sulfur-containing compounds, thiazoles, imidazoles, sulfenamides,thiuramidisulfides, paraquinonedioxime, dibenzoparaquinonedioxime,sulfur; and combinations thereof.

The various crosslinking technologies are described in U.S. Pat. Nos.5,869,591 and 5,977,271, the entire contents of both of which are hereinincorporated by reference. Dual cure systems, which use a combination ofheat, moisture cure, and radiation steps, may be effectively employed.Dual cure systems are disclosed and claimed in U.S. Pat. No. 6,124,370,incorporated herein by reference. For instance, it may be desirable toemploy peroxide coupling agents in conjunction with silane couplingagents, peroxide coupling agents in conjunction with radiation,sulfur-containing coupling agents in conjunction with silane couplingagents, etc.

The blend compositions described above may be converted to foam productsusing any conventional process. Foam products include, for example,extruded thermoplastic polymer foam, extruded polymer strand foam,expandable thermoplastic foam beads, expanded thermoplastic foam beadsor expanded and fused thermoplastic foam beads, and various types ofcrosslinked foams. The foam products may take any known physicalconfiguration, such as sheet, round, strand geometry, rod, solid plank,laminated plank, coalesced strand plank, profiles and bun stock. Thefoam products may be converted into fabricated articles using anyconventional process or method. For example, any one or more ofexpansion, coalescing and welding may be used in making such articles,especially from expandable foam beads. One may also mold expandablebeads into any known configuration that employs foam products,including, but not limited to the foregoing configurations.

Foam forming steps of the process are known in the art. For instance asexemplified by the excellent teachings to processes for making ethylenicpolymer foam structures and processing them in C. P. Park. “PolyolefinFoam”, Chapter 9, Handbook of Polymer Foams and Technology, edited by D.Klempner and K. C. Frisch, Hanser Publishers, Munich, Vienna, New York,Barcelona (1991), which is incorporated here in by reference.

Foams of the present invention may be substantially noncrosslinked. Thefoam structure contains 50 or less, preferably 40 or less, morepreferably 30 or less, even more preferably 20 or less, most preferably10 or less weight percent gel based upon the total weight of foam orpolymer, as measured according to ASTM D-2765-84, Method A.

The foam structure may optionally be substantially cross-linked (i.e.,greater than 50 percent gel based upon the total weight of foam orpolymer, as measured according to ASTM D-2765-84 Method A). The variouscrosslinking technologies are described in U.S. Pat. Nos. 5,869,591 and5,977,271, the entire contents of both of which are herein incorporatedby reference. Dual cure systems, which use a combination of heat,moisture cure, and radiation steps, may be effectively employed. Dualcure systems are disclosed and claimed in U.S. Pat. No. 6,124,370,incorporated herein by reference. For instance, it may be desirable toemploy peroxide coupling agents in conjunction with silane couplingagents, peroxide coupling agents in conjunction with radiation,sulfur-containing coupling agents in conjunction with silane couplingagents, etc. Cross-linking may be induced by addition of a cross-linkingagent. Induction of cross-linking and exposure to an elevatedtemperature to effect foaming or expansion may occur simultaneously orsequentially. If a chemical cross-linking agent is used, it isincorporated into the polymer material in the same manner as thechemical blowing agent. Further, if a chemical cross-linking agent isused, the foamable melt polymer material is heated or exposed to atemperature of preferably less than 150° C. to prevent decomposition ofthe cross-linking agent or the blowing agent and to prevent prematurecross-linking. If radiation cross-linking is used, the foamable meltpolymer material is heated or exposed to a temperature of preferablyless than 160° C. to prevent decomposition of the blowing agent. Thefoamable melt polymer material is extruded or conveyed through a die ofdesired shape to form a foamable structure. The foamable structure isthen cross-linked and expanded at an elevated or high temperature(typically, 150° C.-250° C.) such as in an oven to form a foamstructure. If radiation cross-linking is used, the foamable structure isirradiated to cross-link the polymer material, which is then expanded atthe elevated temperature as described above. The present structure canadvantageously be made in sheet or thin plank form according to theabove process using either cross-linking agents or radiation.

The foam structures of the present invention are optionally made by aconventional extrusion foaming process. The structure is advantageouslyprepared by heating the polymer or blend to form a plasticized or meltpolymer material, incorporating therein a blowing agent to form afoamable gel, and extruding the gel through a die to form the foamproduct. Depending upon the die (with an appropriate number ofapertures) and operating conditions, the product may vary from anextruded foam plank or rod through a coalesced foam strand product, tofoam beads and eventually to chopped strands of foamable beads. Prior tomixing with the blowing agent, the polymer material is heated to atemperature at or above its glass transition temperature or meltingpoint. The blowing agent is optionally incorporated or mixed into themelt polymer material by any means known in the art such as with anextruder, mixer, blender, or the like. The blowing agent is mixed withthe melt polymer material at an elevated pressure sufficient to preventsubstantial expansion of the melt polymer material and to advantageouslydisperse the blowing agent homogeneously therein. Optionally, anucleator is optionally blended in the polymer melt or dry blended withthe polymer material prior to plasticizing or melting. Prior toextruding foamable gel through the die, one typically cools the gel toan optimum temperature. The foamable gel is typically cooled to a lowertemperature to optimize physical characteristics of the foam structure.This temperature, often referred to as the foaming temprature, istypically above each component's polymer glass transition temperature(T_(g)), or for those having sufficient crystallinity, near the peakcrystalline melting temperature (T_(m)). “Near” means at, above, orbelow and largely depends upon where stable foam exists. The temperaturedesirably falls within 30° centigrade (° C.) above or below the T_(m).For foams of the present invention, an optimum foaming temperature is ina range in which the foam does not collapse. The gel may be cooled inthe extruder or other mixing device or in separate coolers. The gel isthen extruded or conveyed through a die of desired shape to a zone ofreduced or lower pressure to form the foam structure. The zone of lowerpressure is at a pressure lower than that in which the foamable gel ismaintained prior to extrusion through the die. The lower pressure isoptionally superatmospheric or subatmospheric (vacuum), but ispreferably at an atmospheric level.

In another embodiment, the resulting foam structure is optionally formedin a coalesced strand form by extrusion of the polymer material througha multi-orifice die. The orifices are arranged so that contact betweenadjacent streams of the molten extrudate occurs during the foamingprocess and the contacting surfaces adhere to one another withsufficient adhesion to result in a unitary foam structure. The streamsof molten extrudate exiting the die take the form of strands orprofiles, which desirably foam, coalesce, and adhere to one another toform a unitary structure. Desirably, the coalesced individual strands orprofiles should remain adhered in a unitary structure to prevent stranddelamination under stresses encountered in preparing, shaping, and usingthe foam. Apparatuses and method for producing foam structures incoalesced strand form are seen in U.S. Pat. Nos. 3,573,152 and4,824,720, both of which are incorporated herein by reference.

Alternatively, the resulting foam structure is conveniently formed by anaccumulating extrusion process and apparatus as seen in U.S. Pat. Nos.4,323,528 and 5,817,705, which are incorporated by reference herein.This apparatus, commonly known as an “extruder-accumulator system”allows one to operate a process on an intermittent, rather than acontinuous, basis. The apparatus includes a holding zone or accumulatorwhere foamable gel remains under conditions that preclude foaming. Theholding zone is equipped with an outlet die that opens into a zone oflower pressure, such as the atmosphere. The die has an orifice that maybe open or closed, preferably by way of a gate that is external to theholding zone. Operation of the gate does not affect the foamablecomposition other than to allow it to flow through the die. Opening thegate and substantially concurrently applying mechanical pressure on thegel by a mechanism (e.g. a mechanical ram) forces the gel through thedie into a zone of lower pressure. The mechanical pressure is sufficientto force foamable gel through the die at a rate fast enough to precludesignificant foaming within the die yet slow enough to minimize andpreferably eliminate generation of irregularities in foamcross-sectional area or shape. As such, other than operatingintermittently, the process and its resulting products closely resemblethose made in a continuous extrusion process.

In this process, low density foam structures having large lateralcross-sectional areas are prepared by: 1) forming under pressure a gelof the polymer or blend material and a blowing agent at a temperature atwhich the viscosity of the gel is sufficient to retain the blowing agentwhen the gel is allowed to expand; 2) extruding the gel into a holdingzone maintained at a temperature and pressure which does not allow thegel to foam, the holding zone having an outlet die defining an orificeopening into a zone of lower pressure at which the gel foams, and anopenable gate closing the die orifice; 3) periodically opening the gate;4) substantially concurrently applying mechanical pressure by a movableram on the gel to eject it from the holding zone through the die orificeinto the zone of lower pressure, at a rate greater than that at whichsubstantial foaming in the die orifice occurs and less than that atwhich substantial irregularities in cross-sectional area or shapeoccurs; and 5) permitting the ejected gel to expand unrestrained in atleast one dimension to produce the foam structure.

The present foam structures may also be formed into foam beads suitablefor molding into articles by expansion of pre-expanded beads containinga blowing agent. The beads may be molded at the time of expansion toform articles of various shapes. Processes for making expanded beads andmolded expanded beam foam articles are described in Plastic Foams, PartII, Frisch And Saunders, pp. 544-585, Marcel Dekker, Inc. (1973) andPlastic Materials, Brydson, 5th Ed., pp. 426-429, Butterworths (1989).Expandable and expanded beads can be made by a batch or by an extrusionprocess, and may be substantially non-crosslinked or substantiallycrosslinked.

The batch process of making expandable beads is similar to manufacturingexpandable polystyrene (EPS). The resulting foam structure is formedinto non-crosslinked foam beads suitable for molding into articles.Discrete resin particles, such as granules made from the blends of thepresent invention, made either by melt blending or in-reactor blending,are impregnated with a blowing agent (and optionally a cross-linkingagent) in an aqueous suspension or in an anhydrous state in a pressurevessel at an elevated temperature and pressure. In the case of theaqueous supsension, the blowing agent (and, optionally, cross-linkingagent) is/are introduced into the liquid medium in which the granulesare substantially insoluble (such as water) at an elevated pressure andtemperature in an autoclave or other pressure vessel. The granules areeither discharged rapidly into an atmosphere or a region of reducedpressure to expand the granules into foam beads or cooled and dischargedas unexpanded beads. In a separate step, the unexpanded beads are heatedto expand them, e.g., with steam or with hot air. This process formaking bead foams is well taught in U.S. Pat. Nos. 4,379,859 and4,464,484, which are incorporated herein by reference.

In a modification of the bead process, styrene monomer is optionallyimpregnated into the suspended pellets of the blend compositions of thepresent invention prior to their impregnation with blowing agent to forma graft interpolymer with the polymer material. The resultinginterpolymer beads are cooled and discharged from the vesselsubstantially unexpanded. The beads are then expanded and molded by anexpanded polystyrene bead molding process within the skill in the art.Such a process of making such polyethylene/polystyrene interpolymerbeads is described for instance in U.S. Pat. No. 4,168,353, which isincorporated herein by reference.

A variation of the foregoing extrusion process readily yields expandablethermoplastic polymer beads. The method tracks with the conventionalfoam extrusion process described above up to the die orifice, which nowcontains one or multiple holes. The variation requires (a) cooling thefoamable gel to a temperature below that at which foaming occurs, (b)extruding cooled gel through a die containing one or more orifices toform a corresponding number of essentially continuous expandablethermoplastic strands, (c) optionally quenching the strands exiting thedie orifice in a cold water bath; and (d) and pelletizing the expandablethermoplastic strands to form expandable thermoplastic beads.Alternatively, the strands are converted to foam beads by cutting thestrands into pellets or granules at the die face and allowing thegranules to expand.

The foam beads can also be prepared by preparing a mixture of thepolymer blend compositions of the present invention, cross-linkingagent, and chemical blowing agent in a suitable mixing device orextruder and form the mixture into pellets, and heat the pellets tocross-link and expand.

In another process for making cross-linked foam beads suitable formolding into articles, the blends of this invention are melted and mixedwith a physical blowing agent in a conventional foam extrusion apparatusto form an essentially continuous foam strand. The foam strand isgranulated or pelletized to form foam beads. The foam beads are thencross-linked by radiation. The cross-linked foam beads may then becoalesced and molded to form various articles as described above for theother foam bead process. Additional teachings to this process are seenin U.S. Pat. No. 3,616,365 and C. P. Park, above publication, pp.224-228.

The foam beads may then be molded by any means known in the art, such ascharging the foam beads to the mold, compressing the mold to compressthe beads, and heating the beads such as with steam to effect coalescingand welding of the beads to form the article. Optionally, the beads maybe impregnated with air or other blowing agent at an elevated pressureand temperature prior to charging to the mold. Further, the beads mayoptionally be heated prior to charging. The foam beads are convenientlythen molded to blocks or shaped articles by a suitable molding methodknown in the art. Some of the methods are taught in U.S. Pat. Nos.3,504,068 and 3,953,558, both incorporated herein by reference.Excellent teachings of the above processes and molding methods are seenin C. P. Park, supra, p. 191, pp. 197-198, and pp. 227-233, U.S. Pat.Nos. 3,886,100, 3,959,189, 4,168,353 and 4,429,059 which areincorporated herein by reference.

The present crosslinked foam structure may also be made into acontinuous plank structure by an extrusion process utilizing a long-landdie as described in GB 2,145,961A. In that process, the polymer,chemical blowing agent and cross-linking agent are mixed in an extruder,heating the mixture to let the polymer cross-link and the blowing agentto decompose in a long-land die; and shaping and conducting away fromthe foam structure through the die with the foam structure and the diecontact lubricated by a proper lubrication material.

The present crosslinked foam structure may be made in bun stock form bytwo different processes. One process involves the use of a cross-linkingagent and the other uses radiation.

The present crosslinked foam structure may be made in bun stock form bymixing the blends of this invention, a cross-linking agent, and achemical blowing agent to form a slab, heating the mixture in a mold sothe cross-linking agent can cross-link the polymer material and theblowing agent can decompose, and expanding by release of pressure in themold. Optionally, the bun stock formed upon release of pressure may bere-heated to effect further expansion.

Foam may be made from cross-linked polymer sheet by either irradiatingpolymer sheet with high energy beam or by heating a polymer sheetcontaining chemical cross-linking agent. The cross-linked polymer sheetis cut into the desired shapes and impregnated with nitrogen in a higherpressure at a temperature above the softening point of the polymer;releasing the pressure effects nucleation of bubbles and some expansionin the sheet. The sheet is re-heated at a lower pressure above thesoftening point, and the pressure is then released to allow foamexpansion.

Blowing agents useful in making the foam structures of the presentinvention include inorganic agents, organic blowing agents and chemicalblowing agents. Suitable inorganic blowing agents include carbondioxide, nitrogen, argon, water, air, sulfur hexafluoride (SF₆) andhelium. Organic blowing agents include aliphatic hydrocarbons having 1-9carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully andpartially halogenated aliphatic hydrocarbons having 1-4 carbon atoms.Aliphatic hydrocarbons include methane, ethane, propane, n-butane,isobutane, n-pentane, isopentane, neopentane, and the like. Aliphaticalcohols include methanol, ethanol, n-propanol, and isopropanol. Fullyand partially halogenated aliphatic hydrocarbons include fluorocarbons,chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbonsinclude methyl fluoride, perfluoromethane, ethyl fluoride,1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161),1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a),1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane,pentafluoroethane (HFC-125), difluoromethane (HFC-32), perfluoroethane,2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane,dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane.Partially halogenated chlorocarbons and chlorofluorocarbons for use inthis invention include methyl chloride, methylene chloride, ethylchloride, 1,1,1-trichloroethane, 1,1-dichloro-1 fluoroethane(HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b),chlorodifluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane(HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fullyhalogenated chlorofluorocarbons include trichloromonofluoromethane(CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane(CFC-113), dichlorotetrafluoroethane (CFC-114),chloroheptafluoropropane, and dichlorohexafluoropropane. Chemicalblowing agents include azodicarbonamide, azodiisobutyro-nitrile, bariumazodicarboxylate, N,N′-dimethyl-N,N′-dinitrosoterephthalamide, andbenzenesulfonhydrazide, 4,4-oxybenzene sulfonyl semicarbazide, andp-toluene sulfonyl semicarbazide, trihydrazino triazine and mixtures ofcitric acid and sodium bicarbonate such as the various products soldunder the name Hydrocerol™ (a product of Boehringer Ingelheim). Any ofthe foregoing blowing agents may be used singly or in combination withone or more other blowing agents. Preferred blowing agents includeisobutane, carbon dioxide, HFC-152a, and mixtures of the foregoing.

The amount of blowing agent incorporated into the polymer melt materialto make a foam-forming polymer gel is from about 0.05 to about 5.0,preferably from about 0.2 to about 3.0, and most preferably from about0.5 to 2.5 gram moles per kilogram of polymer.

Foams are optionally perforated to enhance or accelerate gaseouspermeation exchange wherein blowing agent exits from the foam and airenters into the foam. The resulting perforated foams have definedtherein a multiplicity of channels that are preferably free of directionwith respect to the longitudinal extension of the foam. The channelsextend from one foam surface at least partially through the foam, andsometimes completely through the foam from one external surface toanother external surface. The channels are advantageously present oversubstantially an entire exterior foam surface, preferably with uniformor substantially uniform spacing. Suitable spacing intervals may be upto and including 2.5 centimeters (cm), preferably up to and including1.3 cm. The foams optionally employ a stability control agent of thetype described above in combination with perforation to allowaccelerated permeation or release of blowing agent while maintaining adimensionally stable foam. U.S. Pat. Nos. 5,424,016, 5,585,058, WO92/19439 and WO 97/22455, the teachings of which are incorporated hereinby reference, provide excellent information relative to perforation. Ifdesired, the foams of this invention may be post-treated by any knownmeans to increase foam open cell content. Such post-treatment methodsinclude, without limit, mechanically compressing the foam and expandingthe foam by exposure to steam or hot air.

Foams of the present invention generally have a density less than 900,preferably less than 850, more preferably less than 800 kg/m³, and evenmore preferably from about 5 to about 700 kilograms per cubic meter (inaccordance with ASTM D3575-93, Suffix W, Method B). The foams generallyhave an average cell size of from about 0.001 to about 10.0, preferablyfrom about 0.002 to about 5.0, and more preferably 0.003 to about 3.0millimeters as measured according to the procedures of ASTM D3576. Thepreferred ranges of density and cell size should not be taken aslimiting the scope of this invention.

Foams of the present invention preferably exhibit excellent dimensionalstability. Preferred foams retain 80 or more percent of their initialvolume when measured one month after an initial volume measurementwithin 30 seconds after foam expansion. Volume is measured by anysuitable method such as cubic displacement of water.

The foams of the present invention have an open cell content that rangesfrom 0 to 100 volume percent based on the total volume of foam, asmeasured according to ASTM D2856-94, depending upon component selectionand process condition variations. Foams with an open cell content of 30vol % or less generally fall in a class known as closed cell foams.Those known as open cell foams typically have an open cell contentgreater than 30, preferably greater than 40, and more preferably greaterthan 50 vol %. The open cell content is desirably 100 vol % or less,preferably 95 vol % or less, and more preferably 90 vol % or less.

The foams generally have an Asker-C hardness of ≦80, desirably ≦75, andpreferably ≦70. Hardness measurements of the foams use an Asker Cdurometer for cellular rubber and yarn in accordance with ASTM D2240-97,using a 5 mm diameter spherical indentor.

If the foam is in the shape of a sheet or plank, it has a thickness thatis generally ≧0.5 mm, preferably ≧1 mm and a width that is generally ≧5mm, preferably ≧10 mm. As used herein “thickness” of a foam plank orsheet refers to its smallest cross-sectional dimension (e.g. as measuredfrom one planar surface to an opposing planar surface). When the foam ispresent as a round or rod, it has a diameter that is generally ≧5 mm,preferably ≧10 mm.

The foam has a drop-test optimum C-factor (ASTM-D1596) of ≦6, desirably≦5, and preferably ≦4.

The foams of the present invention may be used in any application wherefoams of comparable density and open or closed cell contents are usedtoday. Such applications include, without limit, cushion packaging (e.g.corner blocks, braces, saddles, pouches, bags, envelopes, overwraps,interleafing, encapsulation) of finished electronic goods such ascomputers, televisions, and kitchen appliances; packaging or protectionof explosive materials or devices; material handling (trays, tote boxes,box liners, tote box inserts and dividers, shunt, stuffing, boards,parts spacers and parts separators); work station accessories (aprons,table and bench top covers, floor mats, seat cushions); automotive(headliners, impact absorption in bumpers or doors, carpet underlayment,sound insulation); flotation (e.g. life jackets, vests and belts);sports and leisure (e.g. gym mats and bodyboards); thermal insulationsuch as that used in building and construction); acoustical insulation(e.g. for appliances and building and construction); gaskets, grommets,seals; sound attenuation for printers and typewriters; display caseinsert; missile container padding; military shell holder; blocking andbracing of various items in transport; preservation and packaging;automotives anti-rattle pads, seals; medical devices, skin contact pads;cushioned pallet; and vibration isolation pad. The foregoing list merelyillustrates a number of suitable applications. Skilled artisans canreadily envision additional applications without departing from thescope or spirit of the present invention.

The film of the present invention may be a monolayer or a multilayerfilm. One or more layers of the film may be oriented or foamed. Amulti-layer film of the present invention may contain one, two or morelayers comprising a blend as defined herein. Preferably, the filmaccording to the invention has a thickness of about 0.5 to about 10mils. Preferably, the present invention pertains to a tough and stifffilm, comprising the grafted blends of this invention. The film of theinvention may be printed. The film of the invention is obtainableaccording to methods known in the art. The film may be made using ablown or a cast film extrusion process, including co-extrusion andextrusion coating. One or more layers of the film may be expanded, forexample with a conventional blowing agent, to make foamed film. One ormore films may be laminated to form a multi-layer structure. The filmsmay be (further) oriented after forming via tenter frame, double-bubbleor other blown film techniques.

In one embodiment, the film of the present invention is an orientedfilm. The term “orientation” as used herein refers to a process ofstretching a hot polymeric article to align the molecular chains in thedirection(s) of stretching. When the stretching is applied in onedirection, the process is called uniaxial orientation; when thestretching is applied in two (perpendicular) directions, the process iscalled biaxial orientation. Orientation can be uniaxial or, preferably,biaxial. Orientation may be accomplished according to conventionalmethods, such as blown film processes, “double-bubble” film processes,cast/tentered film processes or other techniques known in the art toprovide orientation. The oriented films of the invention areparticularly suitable for use in window envelope and relatedapplications.

In another aspect, the present invention relates to a foamed film. Suchfilm is especially suitable for use as label or in thermoformablearticles of manufacture. To make foamed film structures, either physicalor chemical blowing agents may be used. A multilayer film of theinvention comprising one or more foamed layers comprising the graftedblends as defined herein is obtainable according to methods known in theart, for example, using a co-extrusion process. Preferred are two-layeror three-layer films with one or two surface layers and the foamed layerbeing the core layer. The surface layers may or may not comprise thegrafted blends of this invention. In a three layer structure,preferably, the foamed layer is the core or middle layer.

The label film may be constructed from printed, slit to width, rolls offilm with the labels glued to a container, for example a bottle, usingconventional adhesives and glues known to the industry. In addition, thefilms of this invention may be printed, coated with pressure sensitiveadhesives, laminated to release papers or films and applied to bottles,containers or other surfaces by conventional pressure sensitivetechniques. The bottle may be a glass bottle or a PET bottle. Coveringor affixed to a glass bottle, the label may also serve a protectivepurpose. If the bottle is a PET bottle, the preferred label is awrap-around label.

The following examples illustrate, but do not in any way limit the scopeof the present invention.

Test Methods

Melt Index was determined by ASTM D-1238 (190° C./2160 g).

Resin (polymer) density was determined by ASTM D-792, employingArchimede's buoyancy displacement principal.

Flexural Modulus, 1 percent Secant Modulus and 2 percent Secant Moduluswere measured in accordance with ASTM D-790-91, Method 1, Procedure B.The 1% Secant Modulus, 2% Secant Modulus and the Flex Modulus weredetermined using a bar of rectangular cross-section tested using athree-point loading system and a 10 pound load cell.

Melt Tension—The melt tension (in grams) was measured at 160° C. and190° C. using a 2.16 kg load and pulling the strands of molten polymersat 50 rpm around a pulley system for a haul-off rate over a thirtysecond period. The melt tension was this average force.

Melt Strength—The measurements were conducted by pulling strands ofmolten polymers at constant acceleration until draw resonance orbreakage occurred. The experimental set-up consisted of a capillaryrheometer and a Rheotens apparatus as take-up device. The force requiredto uniaxially extend the strands was recorded as a function of thetake-up velocity. The maximum force attained before significant drawresonance or breakage occurred was defined as the melt strength. Thevelocity at which draw resonance or breakage occurred was defined as themelt elongation. The tests were run under the following conditions:

Mass flow rate: 1.35 gram/minute Temperature: 190° C. (unless otherindicated), Capillary length: 41.9 mm Capillary diameter: 2.1 mm Pistondiameter: 9.54 mm Piston velocity: 0.423 mm/s Shear rate: 33.0 s⁻¹Draw-down distance 100 mm (die exit to take-up wheels): Coolingconditions: ambient air Acceleration: 2.4 mm/s²

Upper Service Temperature—A thermomechanical analyzer (TMA) commerciallyavailable from Perkin Elmer Corporation under the trade designationmodel TMA 7 was used to measure the upper service temperature (UST).Probe force of 102 g and heating rate of 5° C./min were used. Each testspecimen was a disk with thickness of 3.3 mm and 7.8 mm diameter,prepared by compression molding at 205° C. and air-cooling to roomtemperature. Temperature at the probe penetration of 1 mm was taken asthe upper service temperature (UST).

The glass transition temperatures (Tg) and peak melting temperature (Tm)were determined by differential scanning calorimetry (DSC). Sample sizewas approximately 5 mg. The following procedure was used for the DSCmeasurements: the sample was placed in a sealed aluminum pan and heatedrapidly from ambient temperature to 180° C. (at a rate of 105° C. per.minute); kept at 180° C. for three minutes to ensure complete melting;cooled at 10° C./min to about −60° C. or 40° C. below the expected Tg;kept at this temperature for three minutes for DSC stabilization; andheated to 150° C. (in general, for ethylenic and alkenyl aromaticpolymers) and 190° C. (for polypropylenes) at a rate of 10° C./min. Thepeak crystallization temperature (Tc) was obtained from the coolingcurve. The peak melting temperature (Tm) was obtained from the meltingcurve (second heat) and was the peak melting temperature. The glasstransition temperature (Tg) was obtained using the half-height methodfrom the second heat DSC curve.

Gel Content was determined by xylene extraction—ASTM D-2765 Procedure“A” to measure the degree of crosslinking of polyethylene. Samples wereimmersed in xylene to extract what was not a gel (or crosslinked). Afterextraction, the sample was then dried and weighed. The resulting datawas converted to percent gel.

EXAMPLES

The following blend components were used in the Examples

LDPE 620I is a low density polyethylene available from The Dow ChemicalCompany

PROFAX PF814 and PROFAX SR256M are polypropylenes available from andtrademarks of Montell.

H704-04 and H700-12 are polypropylene homopolymers available from TheDow Chemical Company

ESI 1 is a substantially random ethylene styrene interpolymer (ESI)having a styrene content of 39 mol % and a melt index, I2, of 1.0 g/10min.

ESI 2 is a substantially random ethylene styrene interpolymer (ESI)having a styrene content of 10 mol % and a melt index, I2, of 1.0 g/10min.

ESI 3 is a substantially random ethylene styrene interpolymer (ESI)having a styrene content of 29 mol % and a melt index, I2, of 0.5 g/10min.

ESI 4 is a substantially random ethylene styrene interpolymer (ESI)having a styrene content of 39 mol % and a melt index, I2, of 1.0 g/10min.

EG8200 refers to AFFINITY™ EG8200 available from and a trademark of TheDow Chemical Company.

DOWLEX™ 2045A is a linear low density polyethylene available from and atrademark of The Dow Chemical Company.

STYRON™ 663 is a general purpose polystyrene available from and atrademark of The Dow Chemical Company.

XU70262.08 refers to general purpose polystyrene of 11 g/10 min meltflow rate and is available from The Dow Chemical Company.

HDPE 10462N, 05862N and DSV10305.00 are high density polyethylenesavailable from The Dow Chemical Company.

HFE-034 is a high density polyethylene available from Mobil ChemicalCompany

LDPE 662I is a low density polyethylene available from The Dow ChemicalCompany

LDPE XSS84812.06 is a low density polyethylene of 0.923 g/cm³ densityand 0.9 dg/min melt index (I2) available from The Dow Chemical Company.

LDPE XUS61528.29 is a linear low density polyethylene of 0.919 g/cm³density and 0.5 dg/min melt index (I2) available from The Dow ChemicalCompany.

ESI's 1-4 were prepared using the coatalysts, cocatalysts andpolymerizations procedures as described in U.S. Pat. No. 6,133,333,columns 14-23 and U.S. Pat. No. 6,136,923, columns 14-19, the contentsof both of which are herein incorporated by reference:

Embodiment 1

Examples 1-24

Different polymers were dry blended with various loadings of4,4′-oxybis(benzene sulfonyl azide) using 4000 ppm mineral oil as atackifying agent. The blends were compounded on a Leistreitz 18 mm twinscrew extruder with L/D=30 at 200 rpm. Temperature settings were: Zone1—130° C.; zone 2—170° C.; zone 3—190° C.; zone 4—190° C.; zone 5—190°C.; die—190° C. Final melt temperatures ranged from 205° C. to 212° C.The same polymer blends were compounded without the azide (but with 4000ppm mineral oil) under the same conditions for comparison.

The data are presented in Table 1. In general, the grafted blendsexhibited improvements (increases) over the same blends without graftingin at least one of the following hardness, melt strength and/upperservice temperature. These data indicate that branching has beenintroduced by grafting of the various polymers.

TABLE 1 Melt Strength and TMA — Temperature (° C.) Melt Elongation atCorresponding to Wt %/Wt % Azide Hardness Indicated Temperatures VariousProbe Penetrations Ex # Component A & B (phr) % Gels Shore A (cN) (mm/s)Temp (° C.) 0.1 mm 0.2 mm 1 mm Comp. Ex. 1 50/50 LDPE 620I & ESI 1 00.09 88.5 27 88 140 95.5 101.3 109.6 Ex. 1 50/50 LDPE 620I & ESI 1 0.10.108 87 31 67 140 104 107 111.5 Ex. 2 50/50 LDPE 620I & ESI 1 0.2 26.0789 44 38 140 105.5 107.8 112.3 Comp. Ex. 2 30/70 LDPE 620I & ESI 1 00.15 78.5 23 158 150 53 60.5 80 Ex. 3 30/70 LDPE 620I & ESI 1 0.05 0.9879 19 124 190 59.4 67.2 89.4 Ex. 4 30/70 LDPE 620I & ESI 1 0.1 1.29 78.532 54 150 87 95.5 109 Ex. 5 30/70 LDPE 620I & ESI 1 0.2 30.07 81.5 50 36150 86.5 92 104.3 Ex. 6 30/70 LDPE 620I & ESI 2 0.1 0.62 84.5 N/A N/AN/A 63.1 68 78.3 Comp. Ex. 3 50/50 LDPE 620I & EG8200 0 1.24 81.5 13 180140 86.5 92 104.2 Ex. 7 50/50 LDPE 620I & EG8200 0.1 1.13 82.5 30 55 14095.5 99.1 107 Ex. 8 50/50 LDPE 620I & EG8200 0.2 5.9 82.5 45 32 140 96.6101.4 107.5 Comp. Ex. 4 30/70 LDPE 620I & EG8200 0 1.28 75.5 6 160 14060 64.1 75.1 Ex. 9 30/70 LDPE 620I & EG8200 0.05 1.09 77 5 390 190 65.468.7 80.2 Ex. 10 30/70 LDPE 620I & EG8200 0.1 1.50 77 21 60 140 70 76 95Ex. 11 30/70 LDPE 620I & EG8200 0.2 2.31 78.5 33 52 140 67.5 73.4 93Comp. Ex. 5 50/50 PROFAX PF814 & ESI 1 0 0.86 95 22 125 180 144 146 151Ex. 12 50/50 PROFAX PF814 & ESI 1 0.1 1.08 96.5 40 23 180 145 147 153Ex. 13 50/50 PROFAX PF814 & ESI 1 0.2 29.50 96 39 28 180 148 150 154.8Comp. Ex. 6 50/50 PROFAX SR256M & ESI 1 0 1.25 90 4 130 180 132.5 135142 Ex. 14 50/50 PROFAX SR256M & ESI 1 0.1 0.08 90.5 62 26 180 132 134.2141.8 Ex. 15 50/50 PROFAX SR256M & ESI 1 0.2 41.86 90.5 60 23 180 132135 144 Comp. Ex. 7 30/70 PROFAX PF814 & ESI 1 0 0.60 88.5 19 137 190 6675 100.5 Ex. 16 30/70 PROFAX PF814 & ESI 1 0.05 1.13 89 30 54 190 102.4111 132.9 Ex. 17 30/70 PROFAX PF814 & ESI 1 0.1 0.46 89.5 37 27 190 112126 145.5 Ex. 18 30/70 PROFAX PF814 & ESI 1 0.2 19.71 89.5 34 26 190 135140 150 Ex. 19 30/70 H704-04 & ESI 1 0.025 1.07 90 12 90 190 68.7 76.195.6 Ex. 20 30/70 H704-04 & ESI 1 0.05 0.62 90.5 24 50 190 77.6 88.8121.6 Ex. 21 30/70 H704-04 & ESI 2 0.05 0.51 91 39 33 190 67.7 71.6 86.5Ex. 22 30/70 H704-04 & ESI 2 0.1 0.75 93.5 N/A N/A N/A 74.1 78.8 119.2Ex. 23 30/70 H704-04 & ESI 2 0.15 1.14 93 N/A N/A N/A 78.7 87.9 133.5Ex. 24 70/30 H704-04 & ESI 2 0.1 1.64 85.5 N/A N/A N/A 154.3 155.7 160.3

Examples 25-33

Different polymers were dry blended with various loadings of4,4′-oxybis(benzene sulfonyl azide) using 4000 ppm mineral oil as atackifying agent. The blends were compounded on a Leistreitz 18 mm twinscrew extruder with L/D=30 at 200 rpm. Temperature settings were: Zone1—130° C.; zone 2—170° C.; zone 3—190° C.; zone 4—190° C.; zone 5—190°C.; die—190° C. Final melt temperatures ranged from 183° C. to 212° C.The same polymer blends were compounded without the azide (but with 4000ppm mineral oil) under the same conditions for comparison. In general,the extruder exit pressure, extruder torque, hardness, melt strength andupper service temperature increased with increasing amounts of theazide. These data in Table 2 indicate that branching had been introducedby coupling or grafting of the various polymers.

TABLE 2 0 ppm 250 ppm 500 ppm 1000 ppm 2000 ppm Ex # Blend Compositionazide* azide azide azide azide Ex. 25 30/70 STYRON* 663/ESI 3 MeltTemperature (° C.) 210 222 223 211 211 Extruder exit pressure (psi) 700850 930 900 1500 Torque (m-g) 5500 5800 6000 6000 6500 % Gels 0.46 1.691.85 1.00 22.14 Shore A hardness 78 82 89 Melt strength (cN) at 170° C.N/A 89 109 Melt elongation (mm/s) at 170° C. N/A 46 31 Temp. topenetrate 0.1 mm in TMA (° C.) 42 58.5 78.7 73 94 Temp. to penetrate 0.2mm in TMA (° C.) 49 67.5 87.7 84 99.5 Temp. to penetrate 1 mm in TMA (°C.) 68 95.4 105.8 106 109 Ex. 26 30/70 STYRON* 663/ESI 1 MeltTemperature (° C.) 210 227 224 211 210 Extruder exit pressure (psi) 650560 675 950 1200 Torque (m-g) 5900 4600 4800 6000 6100 % Gels 0.41 1.990.94 4.64 34.34 Shore A hardness 90 90.5 93 Melt strength (cN) at 170°C. 37 95 99 Melt elongation (mm/s) at 170° C. 580 95 32 Temp. topenetrate 0.1 mm in TMA (° C.) 96 74 75.2 96 99.5 Temp. to penetrate 0.2mm in TMA (° C.) 100 80.8 83.5 100 102.2 Temp. to penetrate 1 mm in TMA(° C.) 107 97.6 102 107 109 Ex. 27 30/70 STYRON* 663/EG8200 MeltTemperature (° C.) 217 213 Extruder exit pressure (psi) 400 500 Torque(m-g) 2000 2400 % Gels 0.56 0.88 Shore A hardness Temp. to penetrate 0.1mm in TMA (° C.) 60.4 61.7 Temp. to penetrate 0.2 mm in TMA (° C.) 67.767.5 Temp. to penetrate 1 mm in TMA (° C.) 75.4 75.3 Ex. 28 30/70XU70262.08/ESI 3 Melt Temperature (° C.) 227 227 Extruder exit pressure(psi) 675 700 Torque (m-g) 5200 5000 % Gels 0.26 0.87 Shore A hardnessTemp. to penetrate 0.1 mm in TMA (° C.) 56 80.7 Temp. to penetrate 0.2mm in TMA (° C.) 63.4 89 Temp. to penetrate 1 mm in TMA (° C.) 84 103.8Ex. 29 50/50 STYRON* 663/ESI 1 Melt Temperature (° C.) 208 210 210Extruder exit pressure (psi) 650 600 1200 Torque (m-g) 5800 5600 6200 %Gels 0.48 0.11 36.75 Shore A hardness 94.5 94.5 94 Melt strength (cN) at170° C. 60 128 98 Melt elongation (mm/s) at 170° C. 525 48 23 Temp. topenetrate 0.1 mm in TMA (° C.) 104.6 105.6 105.6 Temp. to penetrate 1 mmin TMA (° C.) 111 112 113 Ex. 30 50/50 STYRON* 663/ESI 3 MeltTemperature (° C.) 210 209 211 Extruder exit pressure (psi) 710 850 1400Torque (m-g) 5800 5500 6400 % Gels 0.12 0.60 38.19 Shore A hardness 9493.5 95.5 Melt strength (cN) at 190° C. 26 50 68 Melt elongation (mm/s)at 190° C. 700 80 24 Temp. to penetrate 0.1 mm in TMA (° C.) 106 105105.8 Temp. to penetrate 1 mm in TMA (° C.) 112 113 113 Ex. 31 50/50STYRON* XU70262.08/ESI 3 Melt Temperature (° C.) 210 212 195 Extruderexit pressure (psi) 1000 750 1200 Torque (m-g) 6500 5800 6800 % Gels2.71 0.06 30.18 Shore A hardness 94.5 95 96.5 Melt strength (cN) at 190°C. 12 38 90 Melt elongation (mm/s) at 190° C. 440 77 33 Temp. topenetrate 0.1 mm in TMA (° C.) 103 104 104 Temp. to penetrate 1 mm inTMA (° C.) 110 111 112 Ex. 32 50/50 STYRON* XU70262.08/ESI 1 MeltTemperature (° C.) 205 183 206 Extruder exit pressure (psi) 500 750 1150Torque (m-g) 5800 5900 6300 % Gels 0.95 1.36 42.99 Shore A hardness 9494.5 96.5 Melt strength (cN) at 190° C. 11 35 N/A Melt elongation (mm/s)at 190° C. 180 190 N/A Temp. to penetrate 0.1 mm in TMA (° C.) 103 103102 Temp. to penetrate 1 mm in TMA (° C.) 109 110 111 Ex. 33 50/50STYRON* 663/EG8200 Melt Temperature (° C.) 210 209 209 Extruder exitpressure (psi) 500 700 750 Torque (m-g) 5000 5200 5500 % Gels 1.00 12.5240.98 Shore A hardness 94.5 95 95.5 Melt strength (cN) at 140° C. N/A 6525 Melt elongation (mm/s) at 140° C. N/A 33 48 Temp. to penetrate 0.1 mmin TMA (° C.) 99 104.6 104 *Not an Example of Claimed Invention.

Examples 34-36

Mixtures of linear low density polyethylene (LLDPE) and polystyrene(PS), or mixtures of low density polyethylene (LDPE) and PS, were dryblended with 4,4′-oxybis(benzene sulfonyl azide) using 4000 ppm mineraloil as a tackifying agent. The blends were compounded on a Leistreitz 18mm twin screw extruder with L/D=30 at 125 rpm. Temperature settingswere: Zone 1—150° C.; zone 2—175° C.; zone 3—200° C.; zone 4—225° C.;zone 5—225° C.; die—225° C. The comparative example was a film gradeLLDPE that was run with 4000 ppm mineral oil at the same processsettings. The data are presented in Table 3. In general, the graftedblends exhibited comparatively higher melt strength, improved meltelongation and very low gel content.

TABLE 3 Comp. Ex. Ex. Ex. Ex. 8 34 35 36 LLDPE XUS61528.29 (weight %)100 80 50 LDPE 662I (weight %) 20 PS XU70262.08 (weight %) 80 20 50Bisulfonyl azide (ppm) 500 500 500 Drakeol 34 mineral oil (ppm) 40004000 4000 4000 torque m-g 5500 2400 4700 3600 melt temp (° C.) 240 233233 234 die pressure (psi) 750 200 600 375 melt index (g/10 min) 0.5 1.10.22 0.48 Melt strength (cN) at 190° C. 6 26 18 21 Melt elongation(mm/s) at 190° C. 120 315 300 400 Gel Content (%) 0.926

Examples 35-36

Mixtures of linear low density polyethylene (LLDPE) and polystyrene (PS)were dry blended with 4,4′-oxybis(benzene sulfonyl azide) using 4000 ppmmineral oil as a tackifying agent. The blends were compounded on a 30 mmtwin screw extruder at 100 rpm. Temperature settings were: Zone 1—140°C.; zone 2—175° C.; zone 3 -200° C.; zone 4—215° C.; die—225° C. Thecomparative example was a film grade LLDPE that was run with 4000 ppmmineral oil at the same process settings. The data are presented inTable 4. The grafted blends exhibited comparatively higher melt strengthand improved melt elongation.

TABLE 4 Blend Component Comp. Ex 9 Ex 35 Ex 36 DOWLEX 2045A (weight %)100 80 20 PS XU70262.08 (weight %) 20 80 Bisulfonyl azide (ppm) 300 750Drakeol 34 mineral oil (ppm) 4000 4000 4000 Melt Temperature (° C.) 243243 243 Melt Index, I2 (dg/min) N/A 0.67 0.64 Melt strength (cN) at 190°C. 4 10 26 Melt elongation (mm/s) at 190° C. 175 358 340 Gel Content (%)N/A 0.39 0.27 1% Secant Modulus (psi) 58135 297967 2% Secant Modulus(psi) 48894 280322 Flexural Modulus (psi) 70960 298835

Embodiment Two

Examples 37-39

Mixtures of high density polyethylene (HDPE) and low densitypolyethylene (LDPE) were dry blended with 4,4′-oxybis(benzene sulfonylazide) using 4000 ppm mineral oil as a tackifying agent. The blends werecompounded on a Leistreitz 18 mm twin screw extruder with L/D=30 at 200rpm. Temperature settings were: Zone 1—130° C.; zone 2—170° C.; zone3—190° C.; zone 4—190° C.; zone 5—190° C.; die—190° C. The comparativeexamples were the individual polymers, or blends thereof, that were runwith or without azide and with or without mineral oil at the sameprocess settings. The data are presented in Table 5. In general, thegrafted blends exhibited comparatively higher melt strength or melttension and acceptable melt elongation (>25 mm/s).

TABLE 5 Bisulfonyl Mineral Melt Index, 1% secant 2% secant Wt %/Wt %Azide Oil Density I2 Modulus Modulus Component A & B (phr) (wt %) (g/cc)(g/10 min.) psi (kPa) psi (kPa) Comp. Ex. 10 20/80 662I & 10462N 0 0.40%0.9539 4.923 168,162 138,889 Ex. 37 20/80 662I & 10462N 0.075 0.40%0.9522 1.923 Ex. 38 20/80 662I & 10462N 0.1 0.40% 0.9519 1.307 144,491118,883 Ex. 39 20/80 662I & 10462N 0.15 0.40% 0.9534 0.735 Comp. Ex. 11100% HDPE 10462N 0 0% 0.9645 8.606 227,445 190,411 Comp. Ex. 12 100%HDPE 10462N 0 0.40% 0.9624 8.561 222,378 186,173 Comp. Ex. 13 100% HDPE10462N 0.1 0.40% 0.9612 2.849 197,204 165,783 Comp. Ex. 14 100% HDPE10462N 0.2 0.40% 0.9612 1.038 Comp. Ex. 15 100% HDPE 05862N 0 0% 0.96335.162 210,393 176,554 Comp. Ex. 16 100% HDPE 0 0% 0.9550 1.114 161,016132,346 DSV10305.00 Comp. Ex. 17 100% HDPE HFE-034 0 0% 0.9495 2.317169,417 141,752 Melt Melt Melt Melt Melt Melt Flexural Tension TensionStrength At Elongation Strength Elongation Modulus 190° C. 160° C. 190°C. At 190° C. 160° C. 160° C. psi (kPa) (g) (g) (cN) (mm/s) (cN) (mm/s)Comp. Ex. 10 195,144 3.64 5.87 7.7 400 10.5 335 Ex. 37 8.28 9.16 12.7190 15 155 Ex. 38 171,186 N/A N/A 13 115 13.5 125 Ex. 39 N/A N/A 18 9518 100 Comp. Ex. 11 248,627 0.52 0.47 0.7 380 0.9 340 Comp. Ex. 12245,809 0.33 0.37 0.82 245 1 420 Comp. Ex. 13 220,950 3.78 3.9 N/A 1754.5 290 Comp. Ex. 14 N/A 5.69 7.5 90 6.9 360 Comp. Ex. 15 232,033 0.750.79 1 385 1.5 410 Comp. Ex. 16 192,315 2.22 2.34 4.2 175 6.5 335 Comp.Ex. 17 195,794 1.75 2.66 3.2 145 4.2 325

Examples 40-43

A mixture of high density polyethylene (HDPE) and LDPE was dry blendedwith 4,4′-oxybis(benzene sulfonyl azide) using mineral oil as atackifying agent. The blend was compounded on a 40 mm twin screwextruder with at 252 rpm and 175 lb/hr. The temperature profile in theextruder was: Zone 2—169° C.; zone 3—189° C.; zone 4—209° C.; zone5—218° C.; zone 6—227° C.; zone 7—238° C.; zone 8—229° C.; zone 9—216°C,; die—207° C. The final melt temperature was 285° C. The finalproperties of the blend are presented in Table 6.

TABLE 6 Melt Melt I2 Strength Elongation (g/10 Density (cN) at (mm/s) atBlend min) (g/cm³) 190° C. 190° C. Example 20% wt % LDPE 662I 0.800.9528 20 60 40 80 wt % HDPE 10462N - grafted with 0.075 phrBisulfonylazide

This blend was subsequently foamed using an extrusion foaming processwith isobutane as blowing agent. The comparative example was aconventional foam made from LDPE 662I. The properties of the resultingfoams are summarized in Table 7.

TABLE 7 Foam density Open 3D Hardness - (kg/m³) - Cells average 45 daysASTM D3575- (vol %) - cell size ASTM Talc GMS Isobutane 93 Suffix W ASTM(mm) D2240-97 Polymer (phr) (phr) (phr) Fresh 28 days D2856-87 7 daysAsker C Comp. Ex. 17 LDPE 662I 0.5 0.3 12 26.29 29.98 70.7 1.93 26.7 Ex.41 Grafted 0.5 0.3 10 33.34 34.30 42.5 2.31 38.7 Blend of Example 40 Ex.42 Grafted 0.13 0.4 15 23.72 24.21 33.8 1.89 35.0 Blend of Example 40Ex. 43 Grafted 0.13 0.4 20 19.24 20.84 26.9 1.89 36.3 Blend of Example40

Foams of density ranging from about 19 kg/m³ to about 34 kg/m³ weresuccessfully made from grafted blends of HDPE and LDPE. Open cells couldbe varied from 27 to 43 vol %. The cell sizes of the foams ranged fromabout 1.9 to 2.3 mm. The Asker C hardness of the foams made from graftedHDPE/LDPE blends was significantly greater than that of the referencefoam (Comparative Example 17), even at significantly lower foam density.These data indicate that foams made from grafted HDPE/LDPE blends wouldexhibit significantly higher load bearing capability relative to foamsmade from LDPE alone, at similar densities. Or, foams made from graftedHDPE/LDPE blends will have equivalent load bearing capability to LDPEfoams, but at comparatively lower foam density.

Examples 44-45

A mixture of high density polyethylene (HDPE) and LDPE was dry blendedwith 4,4′-oxybis(benzene sulfonyl azide) using 600 ppm mineral oil as atackifying agent. The blend was compounded on a 40 mm twin screwextruder with at 278 rpm and 175 lb/hr. The temperature profile in theextruder was: Zone 2—176° C.; zone 3—200° C.; zone 4—218° C.; zone5—232° C.; zone 6—240° C.; zone 7—250° C.; zone 8—255° C.; zone 9—256°C.; melt temperature was 268° C. The final properties of the blend arepresented in Table 8.

TABLE 8 Melt Melt I2 Strength Elongation (g/10 Density (cN) at (mm/s) atBlend min) (g/cm³) 190° C. 190° C. Ex 44 20% wt % LDPE 662I 0.85 0.953216 89 80 wt % HDPE 10462N 0.1 phr Bisulfonylazide

This blend was subsequently foamed using an extrusion foaming processwith isobutane as blowing agent. The comparative example was aconventional foam made from LDPE 620I. The foams were about 38 mm thick.Some of the foams were subsequently perforated (using needles of about 2mm diameter spaced about 10 mm apart) completely in the verticalthickness direction and aged at room temperature for at least 7 daysbefore testing foam properties, except open cell contents which weremeasured on non-perforated foams. The properties of the foams aresummarized in Table 9.

TABLE 9 Comp. Ex. 18 Ex. 45 Test Property Test Method Units directionFoam from LDPE 620I Foam from Ex. 44 Cell Size mm vertical 2.03 1.82extrusion 1.41 1.55 horizontal 1.64 1.71 average 1.69 1.69 CompressionCreep ASTM D3575- % Linear vertical 22.0 23.1 93 Suffix BB ChangeCompression ASTM D3575- kPa Deflection 93 Suffix D 5% compressionvertical 17.9 13.7 extrusion 33.6 50.2 horizontal 14.4 15.0 10%compression vertical 25.9 26.3 extrusion 48.6 74.2 horizontal 20.6 23.525% compression vertical 42.2 51.3 extrusion 62.7 88.5 horizontal 34.840.4 50% compression vertical 91.8 100.7 extrusion 117.7 138.6horizontal 83.9 87.3 75% compression vertical 255.7 257.7 extrusion342.2 345.1 horizontal 245.8 246.1 Compression Set at ASTM D3575- %Linear vertical 21.7 23.6 50% compression 93 Suffix B Change Densitykg/m³ 25.31 33.64 Open Cell ASTM D2856- Volume % 6.84 50.70 94 ThermalStability ASTM D3575- % Linear extrusion −9.9 −2.2 110° C. 93 Suffix SChange horizontal −7.7 3.3 vertical −2.5 6.7

The thermal stability data indicate that foams made from the graftedHDPE/LDPE blend exhibited better dimensional stability at 110° C. thanthe foam of comparative example 18.

Examples 46-55

A series of grafted blends were prepared from HDPE and LDPE using aLeistreitz 18 mm twin screw extruder with L/D=30 at 100 rpm. Temperaturesettings were: Zone 1—150° C.; zone 2—175° C.; zone 3—200° C.; zone4—225° C.; zone 5—225° C. Final melt temperatures ranged from 237° C. to244° C. The comparative examples were the blends that were run withoutgrafting agent and without mineral oil at the same process settings. Thegrafting agents used were with 4,4′-oxybis(benzene sulfonyl azide) andLupersol™ 130 (2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3), the lattera trademark and product of Elf Atochem.

The data, summarized in Table 10, indicate that grafted blends HDPE/LDPEexhibit increased melt strength and a melt elongation greater than 25mm/s enabling subsequent fabrication of the improved articles of thepresent invention.

TABLE 10 wt %/wt % Melt Melt Component A & Bisulfonyl Gel StrengthElongation Component B & Mineral Azide Lupersol Density Content (cN)(mm/s) Example Component C Oil (%) (phr) 130 (phr) (g/cm3) (%) 190° C.190° C. Comp. 80/20 HDPE 10462N & 0 0 0 0.9538 0.470 6 350 Ex. 19 LDPE662I Comp. 85/15 HDPE 0 0 0 0.9505 0.460 8 200 Ex. 20 DSV10305.00 & LDPE620I Ex. 46 80/20 HDPE 10462N & 0.4 0.05 0 0.9528 0.343 7.5 200 LDPE662I Ex. 47 80/20 HDPE 10462N & 0.4 0.1 0 0.9526 0.292 9 140 LDPE 662IEx. 48 79.4/20/0.6 HDPE 0 0.05 0 0.9532 0.436 7.5 175 10462N & LDPE 662I& EG8200 Ex. 49 78.8/20/1.2 HDPE 0 0.1 0 0.9519 0.582 9 155 10462N &LDPE 662I & EG8200 Ex. 50 78.1/20/1.9 HDPE 0 0.15 0 0.9511 0.382 11 6710462N & LDPE 662I & EG8200 Ex. 51 77.5/20/2.5 HDPE 0 0.2 0 0.9513 0.16913 57 10462N & LDPE 662I & EG8200 Ex. 52 74.7/25/0.3 HDPE 0 0.025 00.9468 0.310 22 43 DSV10305.00 & LDPE 620I & EG8200 Ex. 53 74.4/25/0.6HDPE 0 0.05 0 0.9457 0.410 27 38 DSV10305.00 & LDPE 620I & EG8200 Ex. 5480/20 HDPE 10462N & 0 0 0.1 0.9489 0.680 24 57 LDPE 662I Ex. 55 85/15HDPE 0 0 0.1 0.9478 0.510 46 36 DSV10305.00 & LDPE 620I

Examples 56-61

A series of grafted blends similar in polymer composition to Examples 46and 47 were made using a Leistreitz 18 mm twin screw extruder withL/D=30 at 125 rpm. Temperature settings were: Zone 1—150° C.; zone2—175° C.; zone 3—200° C.; zone 4—225° C.; zone 5—225° C.; die—225° C.The comparative example was LLDPE that was run without grafting agent atthe same process settings. The data are summarized in Table 11.

The grafted blends of Examples 56-58 exhibited higher melt strength andelongation than Comparative Example 21, at relatively higher melt index.That is, the grafted blends of Examples 56-58 would exhibit betterprocessability in applications requiring high melt strength.Additionally, the modulus and upper service temperature of the graftedblends of Examples 56-58 would be significantly greater than that of theLLDPE resin.

The grafted blends of Examples 59-61 exhibited even higher meltstrength, with acceptable melt elongation, at very low melt index. Thegel content was still very low.

TABLE 11 Comp Ex 21 Ex 56 Ex 57 Ex 58 Ex 59 Ex 60 Ex 61 LLDPEXUS61528.29 (wt %) 100 HDPE 10462N (wt %) 80 80 80 80 80 80 LDPE 662I(wt %) 20 20 20 20 20 20 Bisulfonyl azide (ppm) 500 750 1000 Lupersol130 (ppm) 1000 1500 2000 Drakeol 34 mineral oil (ppm) 4000 4000 40004000 4000 4000 4000 torque m-g 5500 3600 3500 3600 6000 6700 7500 melttemp (° C.) 240 235 236 239 239 240 241 die pressure (psi) 750 325 375400 875 1100 1350 Nominal density (g/cm³) 0.919 0.953 0.953 0.953 0.9530.953 0.953 melt index (g/10 min) 0.5 2.71 1.97 1.47 0.07 0.01 0.01 Meltstrength (cN) at 190° C. 6 8 9 24 32 47 Melt elongation (mm/s) at 190°C. 120 175 160 60 44 40 Gel Content (%) 0.74 0.797

The data in Table 11 indicate that grafted blends HDPE/LDPE exhibitincreased melt strength and a melt elongation greater than 25 mm/senabling subsequent fabrication of the improved articles of the presentinvention.

Examples 62-65

A series of grafted blends were prepared from HDPE and LDPE using a 30mm twin screw extruder at 100 rpm. Temperature settings were: Zone1—140° C.; zone 2—175° C.; zone 3—200° C.; zone 4—215° C.; zone 5—220°C.; die—225° C. Comparisons were made (Comparative Example 22) and HDPE(Comparative Example 23) of similar melt index. The data are summarizedin Table 12.

The grafted blend of Example 62 exhibited significantly higher modulusthan Comparative Example 22 of similar melt index (0.8 dg/min) andidentical melt strength (12 cN).

The grafted blend of Example 65 exhibited significantly higher meltstrength than Comparative Example 23 of similar melt index (1 dg/min)and density (0.953-0.955 g/cm³). That is, the grafted blends of thisinvention exhibit processability similar to branched resins (e.g., LDPE)with modulus and upper service temperature similar to that of linearpolyethylene.

TABLE 12 Comp Ex 22 Comp Ex 23 Ex 62 Ex 63 Ex 64 Ex 65 LDPE XSS84812.06100 HDPE DSV10305.00 (wt %) 100 HDPE 10462N (wt %) 80 80 80 80 LDPE 662I(wt %) 20 20 20 LDPE 620I 20 Bisulfonyl azide (ppm) none none 1000Lupersol 130 peroxide (ppm) none none 150 300 300 Drakeol 34 mineral oil(ppm) none none 4000 4000 4000 4000 Melt Temperature (° C.) N/A N/A 243242 243 241 Melt Index, I2 (dg/min) 0.83 1.09 0.82 1.71 0.64 1.04 Meltstrength (cN) at 190° C. 12 4.3 12 9 13 8 Melt elongation (mm/s) at 190°C. 180 110 140 225 95 170 Gel Content (%) N/A 0.95 0.41 0.45 0.44 0.39Density (g/cm³) 0.9236 0.9547 0.9531 0.9523 0.9517 0.9529 1% SecantModulus (psi) 54842 166823 136301 136360 129390 135065 2% Secant Modulus(psi) 47371 140395 117612 115239 109004 114069 Flexural Modulus (psi)62903 195851 145518 154459 146327 154952

Example 66

The grafted blend of Example 44 was further blended with an ethylenestyrene interpolymer (ESI 4) at a 70:30 wt % ratio and subsequentlyfoamed using an extrusion foaming process with isobutane as blowingagent. The comparative example was a conventional foam made from LDPE620I. The foams were about 38 mm thick. Some of the foams weresubsequently perforated (using needles of about 2 mm diameter spacedabout 10 mm apart) completely in the vertical/thickness direction andaged at room temperature for at least 7 days before testing foamproperties, except open cell contents which were measured onnon-perforated foams. The properties of the foams are summarized inTable 13.

TABLE 13 Ex 66 Foam Made from Comp Ex 24 70/30 Blend of Foam madeGrafted Blend of from LDPE Example 44 & Test Property Test Method UnitsDirection 620I ESI 4 Cell Size mm Vertical 2.03 1.82 Extrusion 1.41 1.41Horizontal 1.64 1.47 Average 1.69 1.57 Compression ASTM kPa DeflectionD3575-93 Suffix D 5% compression Vertical 17.9 14.3 Extrusion 33.6 31.2Horizontal 14.4 13.6 10% compression Vertical 25.9 21.2 Extrusion 48.642.7 Horizontal 20.6 18.8 25% compression Vertical 42.2 35.5 Extrusion62.7 52.6 Horizontal 34.8 28.1 50% compression Vertical 91.8 71.0Extrusion 117.7 89.3 Horizontal 83.9 59.5 75% compression Vertical 255.7183.7 Extrusion 342.2 229.9 Horizontal 245.8 165.9 Compression Set ASTM% Linear Vertical 21.7 18.4 at 50% D3575-93 Change Compression Suffix BDensity kg/m³ 25.31 25.47 Open Cells ASTM D2856-94 Volume % 6.84 40.62Thermal Stability ASTM D3575-93 % Linear Extrusion −9.9 −2.8 at 110° C.Suffix S Change Horizontal −7.7 −3.1 Vertical −2.5 1.7

Blending ESI with a grafted HDPE/LDPE blend results in foams thatexhibit lower compression set and better thermal stability (dimensionalstability) at C110° than the foam of comparative example 24.

Embodiment 3

Examples 67-69

Mixtures of linear low density polyethylene (LLDPE) and polypropylene(PP), or mixtures of low density polyethylene (LDPE) and PP, were dryblended with various loadings of 4,4′-oxybis(benzene sulfonyl azide)using 4000 ppm mineral oil as a tackifying agent. The blends werecompounded on a Leistreitz 18 mm twin screw extruder with L/D=30 at 125rpm. Temperature settings were: Zone 1—150° C.; zone 2—175° C.; zone3—200° C.; zone 4—225° C.; zone 5—225° C.; die—225° C. The comparativeexample was a film grade LLDPE that was run with 4000 ppm mineral oil atthe same process settings. The data are presented in Table 14. Thegrafted blends exhibited comparatively higher melt strength andacceptable melt elongation (>25 mm/s). Furthermore, the grafted blendsof Examples 67-68 are expected to exhibit relatively higher modulus andupper service temperature than Comparative Example 25 because of thepolypropylene used.

TABLE 14 Comp Ex 25 Ex 67 Ex 68 Ex 69 LLDPE XUS61528.29 (wt %) 100 80 80LDPE 662I (wt %) 80 PP H700-12 (wt %) 20 20 20 Bisulfonyl azide (ppm)250 500 500 Drakeol 34 mineral oil (ppm) 4000 4000 4000 4000 torque m-g5500 4200 5000 3500 melt temp (° C.) 240 231 241 237 die pressure (psi)750 500 700 600 melt index (g/10 min) 0.5 0.36 0.1 0.13 Melt strength(cN) at 190° C. 6 10 23 40 Melt elongation (mm/s) at 120 100 58 38 190°C. Gel content (%) 0.501 0.771

Example 70

A mixture of linear low density polyethylene (LLDPE) and polypropylene(PP) was dry blended with 4,4′-oxybis(benzene sulfonyl azide) using 4000ppm mineral oil as a tackifying agent. The blend was compounded on a 30mm twin screw extruder at 100 rpm. Temperature settings were: Zone1—140° C.; zone 2—175° C.; zone 3—200° C.; zone 4—215° C.; zone 5—220°C.; die—225° C. The comparative example was a film grade LLDPE that wasrun with 4000 ppm mineral oil at the same process settings. The data arepresented in Table 15. The grafted blends exhibited comparatively highermelt strength and acceptable melt elongation (>25 mm/s).

TABLE 15 Comp Ex 26 Ex 70 DOWLEX 2045A (wt %) 100 80 PP H700-12 (wt %)20 Bisulfonyl azide (ppm) 300 Drakeol 34 mineral oil (ppm) 4000 4000Melt Temperature (° C.) 243 240 Melt Index, I2 (dg/min) N/A 0.59 Meltstrength (cN) at 190° C. 4 8 Melt elongation (mm/s) at 190° C. 175 100Gel Content (%) N/A 0.41 1% Secant Modulus (psi) 57495 2% Secant Modulus(psi) 50412 Flexural Modulus (psi) 64321

What is claimed is:
 1. A grafted blend composition comprising, (A) oneor more homopolymers or interpolymers with peak crystalline meltingtemperature (Tm) and/or or glass transition temperature (Tg by DSC) of90° C. or more; (B) one or more homopolymers or interpolymers with peakcrystalline melting temperature (Tm) and/or glass transition temperature(Tg by DSC) of 80° C. or less; and (C) at least one coupling agent; andwherein 1) the upper service temperature of said grafted blend isgreater than about 80° C.; wherein Components A and B in combinationcomprise: a) two or more substantially random interpolymers; b) two ormore olefinic polymers; c) two or more alkenyl aromatic polymers; d) oneor more substantially random interpolymers and one or more olefinicpolymers; e) one or more substantially random interpolymers and one ormore alkenyl aromatic polymers; f) one or more olefinic polymers and oneor more alkenyl aromatic polymers; g) one or-more substantiallyinterpolymers and one or more alkenyl aromatic polymers; or h) one ormore olefinic polymers, one or more substantially random interpolymersand one or more alkenyl aromatic polymers; 2) the gel content of saidgrafted blend is 50 percent or less (as determined by insolubility ofthe gels in boiling xylene when tested according to ASTM D-2765A-84); 3)said grafted blend composition exhibits at least one of the followingimprovements relative to the same blend in the absence of Component C;(a) the melt strength is increased by 5% or more; and/or (b) the upperservice temperature is increased by 0.5° C. or more.
 2. The graftedblend composition of claim 1 wherein A) Component A is present in anamount of from about 0.5 to about 99.5 percent by weight (based on thecombined weights of Components A, B and C); B) Component B is present inan amount of from about 0.5 to about 99.5 percent by weight (based onthe combined weights of Components A, B and C) and C) Component C is oneor more of poly(sulfonyl)azides and/or peroxides; and wherein 1)Components A and B are selected from the group consisting of thesubstantially random interpolymers, the olefinic polymers; the alkenylaromatic polymers, or any combination thereof; 2) the upper servicetemperature of said grafted blend is greater than about 85° C.; 3) thegel content of said grafted blend is 40 percent or less (as determinedby insolubility of the gels in boiling xylene when tested according toASTM D-2765A-84); and 4) said grafted blend composition exhibits atleast one of the following improvements relative to the same blend inthe absence of Component C; (a) the melt strength is increased by 10% ormore; and/or (b) the upper service temperature is increased by 1.0° C.or more.
 3. The grafted blend composition of claim 1 wherein A)Component A is present in an amount of from about 5 to about 95 percentby weight (based on the combined weights of Components A, B and C); B)Component B is present in an amount of from about 5 to about 95 percentby weight (based on the combined weights of Components A, B and C) andC) Component C is one or more of poly(sulfonyl)azides and/or peroxides;and wherein 1) Components A and B are selected from the group consistingof an ethylene homopolymer or copolymer, a propylene homopolymer orcopolymer, a styrene homopolymer or copolymer, a substantially randomethylene/styrene or ethylene/α-olefin/styrene interpolymer or acombination thereof; 2) the upper service temperature of said graftedblend is greater than about 90° C.; 3) the gel content of said graftedblend is 30 percent or less (as determined by insolubility of the gelsin boiling xylene when tested according to ASTM D-2765A-84); and 4) saidgrafted blend composition exhibits at least one of the followingimprovements relative to the same blend in the absence of Component C;(a) the melt strength is increased by 10% or more; and/or (b) the upperservice temperature is increased by 1.5° C. or more.
 4. The graftedblend composition of claim 1 wherein A) Component A is present in anamount of from about 10 to about 90 percent by weight (based on thecombined weights of Components A, B and C); B) Component B is present inan amount of from about 10 to about 90 percent by weight (based on thecombined weights of Components A, B and C) and C) Component C is one ormore of poly(sulfonyl)azides and/or peroxides; and wherein 1) ComponentsA and B are selected from the group consisting of an ethylenehomopolymer or copolymer, a propylene homopolymer or copolymer, astyrene homopolymer or copolymer, a substantially randomethylene/styrene or ethylene/(α-olefin/styrene interpolymer or acombination thereof; 2) the upper service temperature of said graftedblend is greater than about 90° C.; 3) the gel content of said graftedblend is 20 percent or less (as determined by insolubility of the gelsin boiling xylene when tested according to ASTM D-2765A-84); and saidgrafted blend composition exhibits at least one of the followingimprovements relative to the same blend in the absence of Component C;(a) the melt strength is increased by 10% or more; and/or (b) the upperservice temperature is increased by 1.5° C. or more relative to the sameblend in the absence of Component C.
 5. The grafted blend composition ofclaim 4 wherein A) Component A is present in an amount of from about 10to about 60 percent by weight (based on the combined weights ofComponents A, B and C) and B) Component B is present in an amount offrom about 40 to about 90 percent by weight (based on the combinedweights of Components A, B and C); and and wherein a) the gel content ofsaid grafted blend is 10 percent or less; and b) the upper servicetemperature of said grafted blend composition is increased by 5° C. ormore relative to the same blend in the absence of Component C.
 6. Agrafted blend composition comprising (A) a blend of; 1) one or morelinear or substantially linear ethylene homopolymers or interpolymersand one or more branched ethylene homopolymers or interpolymers; 2) oneor more linear or substantially linear ethylene homopolymers orinterpolymers and one or more substantially random interpolymers; or 3)one or more linear or substantially linear ethylene homopolymers orinterpolymers, one or more branched ethylene homopolymers orinterpolymers and one or more substantially random interpolymers; and(B) one or more coupling agents; and wherein said grafted blendcomposition has a) a melt strength, greater than about 8 cN; b) a meltelongation of 20 mm/s or greater; c) a flexural modulus of 80,000 psi orgreater; and d) a gel content which is 50 percent or less, as determinedby insolubility of the gels in boiling xylene when tested according toASTM D-2765A-84.
 7. The grafted blend composition of claim 6 whereinsaid grafted blend composition has a) a melt strength, greater thanabout 10 cN, b) a melt elongation of 25 mm/s or greater; c) a flexuralmodulus of 100,000 psi or greater; and d) a gel content which is 40percent or less, as determined by insolubility of the gels in boilingxylene when tested according to ASTM D-2765A-84.
 8. The grafted blendcomposition of claim 6 wherein said grafted blend composition has a) amelt strength, greater than about 15 cN, b) a melt elongation of 30 mm/sor greater; c) a flexural modulus of 110,000 psi or greater, and d) agel content which is 30 percent or less, as determined by insolubilityof the gels in boiling xylene when tested according to ASTM D-2765A-84.9. The grafted blend composition of claim 8 wherein; A) said polymerblend Component (A) comprises a blend of HDPE with LDPE; B) and saidcoupling agent, Component (B) is on azide or a peroxide or a combinationthereof.
 10. The grafted blend composition of claim 8 wherein; A) saidpolymer blend Component (A) comprises a blend of heterogeneous orhomogeneous LLDPE with LDPE; and B) said coupling agent, Component (B)is an azide or a peroxide or a combination thereof.
 11. The graftedblend composition of claim 8, wherein A) said polymer blend Component(A) comprises a blend of a substantially linear ethylene homopolymer orinterpolymer with LDPE and said coupling agent; and B) Component (B) isan azide or a peroxide or a combination thereof.
 12. A grafted blendcomposition which has a melt index, I2, of about 0.05 to about 10 g/10min comprising; A) from 55 to 90 wt percent (based on the combinedweights of component A and B) of a linear or substantially linearethylene homopolymer or interpolymer, having a density of greater than0.9450 g/cm³; B) from 10 to 45 wt percent (based on the combined weightsof component A and B) of a branched ethylene homopolymer or interpolymerhaving a melt strength of greater than 5 cN; and C) from 0.005 wtpercent to about 0.2 wt % (based on the combined weights of A and B) ofa coupling agent; and D) wherein the melt strength of said grafted blendis greater than 5 cN.
 13. A grafted blend composition comprising, (A)one or more olefinic polymers other than polypropylene; (B) one or morepropylene homopolymers or interpolymers; and (C) at least one couplingagent; and wherein said grafted blend has 1) a gel content which is 50percent or less, as determined by insolubility of the gels in boilingxylene when tested according to ASTM D-2765A-84; 2) a melt elongationgreater than or equal to about 20 mm/s, 3) a melt strength greater thanabout 5 cN; and 4) a flexural modulus of 50,000 psi or greater.
 14. Thegrafted blend composition of claim 13 wherein; 1) said gel content is 40percent or less, as determined by insolubility of the gels in boilingxylene when tested according to ASTM D-2765A-84; 2) said melt elongationis greater than or equal to about 25 mm/s; 3) said melt strength isgreater than about
 10. 15. The grafted blend composition of claim 13comprising, wherein 1) said coupling agent is an azide or a peroxide ora combination thereof; 2) said gel content is 30 percent or less asdetermined by insolubility of the gels in boiling xylene when testedaccording to ASTM D-2765A-84; and 3) said melt strength is greater thanabout 15 cN.
 16. A blend comprising from about 0.1 to about 99.9 wtpercent of the grafted blend composition of claims 1, 6, and 13; andfurther comprising from about 0.1 to about 99.9 wt percent of athermoplastic polymer.
 17. A fabricated article comprising the graftedblend composition of claims 1, 6, 13 and 16 in the form of a film,fiber, blow molded article or extrusion coating.
 18. A process forpreparing grafted blend compositions comprising a coupling agent insolid form and a polymer or polymer blend composition, said processcomprising; 1) mixing said polymer or polymer blend with a tackifier; 2)tumble blending the mixture from step 1 with said coupling agent; and 3)extruding the resulting mixture at a temperature at which the couplingagent is activated.
 19. A process for preparing grafted blendcomposition comprising a coupling agent in liquid form and a polymer orpolymer blend composition, said process comprising; 1) mixing saidcoupling agent with a tackifier, and 2) tumble blending the mixture fromstep 1 with said polymer or polymer blend composition; and 3) extrudingthe resulting mixture at a temperature at which the coupling agent isactivated.
 20. The process of claim 18 or 19, wherein said tackifier isa mineral oil and is present in an amount of from about 0.2 to about 2percent by weight (based on the weight of the final grafted blendcomposition).
 21. A process for preparing grafted blend compositioncomprising a coupling agent and resin comprising a polymer blendcomposition, said process comprising; 1) preparing a mixture of thecoupling agent; and a resin comprising one of the components of saidpolymer blend, and extruding the resulting mixture at a temperature atwhich the coupling agent is not activated; 2) adding the remainingcomponent(s) of said polymer blend composition, other than that used instep (1), to the mixture from step (1), in an amount required to givethe final desired concentration of coupling agent (based on the weightof the final grafted blend composition); and 3) extruding the mixturefrom step 3 at a temperature at which the coupling agent is activated.